user13093: I think the question is simple, why is it important to maintain a single platform for clearly distinct sects of Buddhism ( Theravada and Mahayana )? 
I know there is also Vajrayāna tradition but I think that wouldn't cause the same issue if included with Mahayana.
Most of the responses given here are in the form of contention/competition between these sects, and for most people who don't have a deeper knowledge of these traditions, the answers could at times be confusing to say the least. 
Clearly, the higher goal for these traditions is not the same, see here for example responses given for a recent question about craving by @Sankha Kulathantille and @ Andrei Volkov.   
Why not maintain a distinct SE section for each tradition? 

user254: I don't think it's possible (i.e. I doubt that Stack Exchange would support it, and/or that sufficiently many users would support it).
I guess that, to do it, people (i.e. you) would need to:

Propose new (separate) sites on "Area 51"
Get a lot of support for that proposal (which may be difficult or impossible -- it was difficult, or took a long time, to get enough support for a single site)


Note that other "religion" SE sites don't have separate sites for separate sects or traditions:

Chritianity
Hinduism
Islam
Judaism


Many of the policies discussed on this meta-site were meant to let the different traditions co-exist on one site -- see the topic tagged traditions.

I don't know much about Stack Exchange's policies on this topic (but as I said I guess they wouldn't be keen to split the site, and/or would need a lot of persuading, or rather might require the normal "Area 51" process).
There's a blog post from 2010, Merging Season, about how big a site should be (e.g. whether it should be one site or several).
To start a new (Beta) site I think you need (a minimum) 200 users committing to the proposal on Area 51 (or 100 users who are already active on other SE sites).

I'm not even sure the sects are clearly distinct: you can identify differences but I think they have a lot in common too -- see for example What teachings do all schools of Buddhism share?
Since you mentioned Andrei and Sankha, I also note the interchange in these comments a few years ago:

Could you mention that your answer is based in Theravada Buddhism? Thank you. – Lanka
@Lanka Theravada Buddhists don't really recognize other schools. Mostly historians do that. So it's just Buddhism for us. – Sankha Kulathantille
And we do recognize other schools, it's all Buddhism for us :) – Andrei Volkov♦

Even where there are two traditions I believe that at least some people are interested in both.

user471: I disagree that Buddhism SE should be split into different sects for the following reasons.
Firstly, the fundamental doctrinal core of the different sects or traditions are the same.
In Christianity, all major denominations accept the Nicene Creed. In Islam, all major sects accept the shahada.
Similarly, all major Buddhist schools accept the Four Noble Truths, the Three Marks of Existence, the Noble Eightfold Path, Dependent Origination and the Three Refuges.
Secondly, certain sects or traditions may have additional philosophical content that other sects or traditions do not accept, but are nevertheless ultimately not contradictory to the fundamental doctrinal core.
I've made some analysis of this in this answer.
Thirdly, there are definitely many questions that are tradition-agnostic or sect-agnostic. I think more than half of the questions we have on Buddhism SE are tradition-agnostic or sect-agnostic.
Fourthly, there are some hybrid experts both on this site and those outside this site (who are used as references), who can cater to multiple traditions simultaneously. We would benefit from their diverse and cross-traditional perspectives.
I would completely agree with Lanka's proposal here as the solution to your problem:

In the past we discussed writing a short sentence in the beginning of
  an answer, to state which tradition the answer belongs to. I myself
  forget to do that sometimes. I guess we could be better at stating
  that to avoid confusion for new-comers.


user-1: I think one of the forces of our site is the diversity and the fact that Buddhism SE harbors all traditions within Buddhism.
We have tags that users can attach to their question, if they want an answer from a particular tradition. If no tag is used, the question can receive answers from all traditions.
Please bear in mind that many of the users on the site know each other and pretty much know which tradition an answer is based in, even when not stated.
In the past we discussed writing a short sentence in the beginning of an answer, to state which tradition the answer belongs to. I myself forget to do that sometimes. I guess we could be better at stating that to avoid confusion for new-comers.
Regarding a separation of Buddhism SE into different traditions, I vote against that. I think that's not conducive to the interfaith dialogue. Also having different traditions give fresh inputs or sometimes another tradition explains a particular Buddhist verse, term or doctrine better than another tradition. That especially goes for the Tibetan descriptions of the Mind, which are some of the best I've ever read.
Liberation from Samsara, doing good, helping others, cultivating/purifying the mind, are goals that all traditions value and work towards. Splitting Buddhism SE would directly oppose those goals.

13093: <p>I think the question is simple, why is it important to maintain a single platform for clearly distinct sects of Buddhism ( Theravada and Mahayana )? </p>

<p>I know there is also Vajrayāna tradition but I think that wouldn't cause the same issue if included with Mahayana.</p>

<p>Most of the responses given here are in the form of contention/competition between these sects, and for most people who don't have a deeper knowledge of these traditions, the answers could at times be confusing to say the least. </p>

<p>Clearly, the higher goal for these traditions is not the same, see <a href="https://buddhism.stackexchange.com/questions/25325/why-does-the-third-noble-truth-not-include-the-ten-fetters">here</a> for example responses given for a recent question about craving by @Sankha Kulathantille and @ Andrei Volkov.   </p>

<p>Why not maintain a distinct SE section for each tradition? </p>
 254: <p>I don't think it's possible (i.e. I doubt that Stack Exchange would support it, and/or that sufficiently many users would support it).</p>
<p>I guess that, to do it, people (i.e. you) would need to:</p>
<ol>
<li>Propose new (separate) sites on &quot;<a href="http://area51.stackexchange.com/faq">Area 51</a>&quot;</li>
<li>Get a lot of support for that proposal (which may be difficult or impossible -- it was difficult, or took a long time, to get enough support for a single site)</li>
</ol>
<hr />
<p>Note that other &quot;religion&quot; SE sites don't have separate sites for separate sects or traditions:</p>
<ul>
<li><a href="https://christianity.stackexchange.com/">Chritianity</a></li>
<li><a href="https://hinduism.stackexchange.com/">Hinduism</a></li>
<li><a href="https://islam.stackexchange.com/">Islam</a></li>
<li><a href="https://judaism.stackexchange.com/">Judaism</a></li>
</ul>
<hr />
<p>Many of the policies discussed on this meta-site were meant to let the different traditions co-exist on one site -- see the topic tagged <a href="/questions/tagged/traditions" class="post-tag" title="show questions tagged &#39;traditions&#39;" rel="tag">traditions</a>.</p>
<hr />
<p>I don't know much about Stack Exchange's policies on this topic (but as I said I guess they wouldn't be keen to split the site, and/or would need a lot of persuading, or rather might require the normal &quot;Area 51&quot; process).</p>
<p>There's a blog post from 2010, <a href="https://stackoverflow.blog/2010/09/17/merging-season/">Merging Season</a>, about how big a site should be (e.g. whether it should be one site or several).</p>
<p>To start a new (Beta) site I think you need (a minimum) 200 users committing to the proposal on Area 51 (or 100 users who are already active on other SE sites).</p>
<hr />
<p>I'm not even sure the sects are clearly distinct: you can identify differences but I think they have a lot in common too -- see for example <a href="https://buddhism.stackexchange.com/q/1487/254">What teachings do all schools of Buddhism share?</a></p>
<p>Since you mentioned Andrei and Sankha, I also note the interchange in <a href="https://buddhism.stackexchange.com/questions/10763/if-a-buddhist-should-not-kill-a-mouse-living-in-their-home-what-justification-d/10766#comment16597_10766">these comments</a> a few years ago:</p>
<blockquote>
<p>Could you mention that your answer is based in Theravada Buddhism? Thank you. – Lanka</p>
<p>@Lanka Theravada Buddhists don't really recognize other schools. Mostly historians do that. So it's just Buddhism for us. – Sankha Kulathantille</p>
<p>And we do recognize other schools, it's all Buddhism for us :) – Andrei Volkov♦</p>
</blockquote>
<p>Even where there are two traditions I believe that at least some people are interested in both.</p>
 471: <p>I disagree that Buddhism SE should be split into different sects for the following reasons.</p>

<p>Firstly, the fundamental doctrinal core of the different sects or traditions are the same.</p>

<p>In Christianity, all major denominations accept the Nicene Creed. In Islam, all major sects accept the shahada.</p>

<p>Similarly, all major Buddhist schools accept the Four Noble Truths, the Three Marks of Existence, the Noble Eightfold Path, Dependent Origination and the Three Refuges.</p>

<p>Secondly, certain sects or traditions may have additional philosophical content that other sects or traditions do not accept, but are nevertheless ultimately not contradictory to the fundamental doctrinal core.</p>

<p>I've made some analysis of this in <a href="https://buddhism.stackexchange.com/a/24772/471">this answer</a>.</p>

<p>Thirdly, there are definitely many questions that are tradition-agnostic or sect-agnostic. I think more than half of the questions we have on Buddhism SE are tradition-agnostic or sect-agnostic.</p>

<p>Fourthly, there are some hybrid experts both on this site and those outside this site (who are used as references), who can cater to multiple traditions simultaneously. We would benefit from their diverse and cross-traditional perspectives.</p>

<p>I would completely agree with Lanka's proposal here as the solution to your problem:</p>

<blockquote>
  <p>In the past we discussed writing a short sentence in the beginning of
  an answer, to state which tradition the answer belongs to. I myself
  forget to do that sometimes. I guess we could be better at stating
  that to avoid confusion for new-comers.</p>
</blockquote>
 -1: <p>I think one of the forces of our site is the diversity and the fact that Buddhism SE harbors all traditions within Buddhism.</p>

<p>We have <em>tags</em> that users can attach to their question, if they want an answer from a particular tradition. If no tag is used, the question can receive answers from all traditions.</p>

<p>Please bear in mind that many of the users on the site know each other and pretty much know which tradition an answer is based in, even when not stated.</p>

<p>In the past we discussed writing a short sentence in the beginning of an answer, to state which tradition the answer belongs to. I myself forget to do that sometimes. I guess we could be better at stating that to avoid confusion for new-comers.</p>

<p>Regarding a separation of Buddhism SE into different traditions, I vote against that. I think that's not conducive to the interfaith dialogue. Also having different traditions give fresh inputs or sometimes another tradition explains a particular Buddhist <em>verse, term or doctrine</em> better than another tradition. That especially goes for the Tibetan descriptions of the Mind, which are some of the best I've ever read.</p>

<p>Liberation from Samsara, doing good, helping others, cultivating/purifying the mind, are goals that all traditions value and work towards. Splitting Buddhism SE would directly oppose those goals.</p>
