user122: Imagine the following:
You are a new user with 1 rep. You want to ask a question about a manga/anime, that has no tag yet (in my example: Chaos;Head, tag would be chaos-head). How should such a user tag the question? He can't use the tag for the manga/anime, because it doesn't exist yet/he can't create it, he can't ask at meta or in the chat, because he hasn't enough rep yet and he can't use a generic tag like anime, because they're blocked. What should the new user do?
Should new users have the possibility to create new tags for new series? I think that's a bad idea, but it's the only one I could think of.

user15: The rep limit is to avoid that any drive-by user can create a tag (even non-sensical or offensive wordings).
It's a protection for us. If a new user wants a retag, they can simply ask so in a comment. Any regular user will add the tag. 

user27: It's a bad idea, simply because a new user doesn't know how the system works. He doesn't know what is the accepted format for tags in Stack Exchange in general.
Even a user who's active on another site (And thus gets a 100 point bonus), doesn't know what the accepted tag scheme on this specific site is.
If a user wants a question tagged with a specific anime which doesn't exist, the expected behavior is:

Find a tag which closely matches what he wants
Either wait for a retag by a high-rep user.
Even better, flag the question for retagging by a moderator.

I understand the system is problematic, but allowing new users to arbitrarily add tags induces more problems than it would solve.

122: <p>Imagine the following:<br>
You are a new user with 1 rep. You want to ask a question about a manga/anime, that has no tag yet (in my example: Chaos;Head, tag would be <a href="https://anime.stackexchange.com/questions/tagged/chaos-head" class="post-tag" title="show questions tagged &#39;chaos-head&#39;" rel="tag">chaos-head</a>). How should such a user tag the question? He can't use the tag for the manga/anime, because it doesn't exist yet/he can't create it, he can't ask at meta or in the chat, because he hasn't enough rep yet and he can't use a generic tag like <a href="https://anime.stackexchange.com/questions/tagged/anime" class="post-tag" title="show questions tagged &#39;anime&#39;" rel="tag">anime</a>, because they're blocked. What should the new user do?</p>

<p>Should new users have the possibility to create new tags for new series? I think that's a bad idea, but it's the only one I could think of.</p>
 15: <p>The rep limit is to avoid that any drive-by user can create a tag (even non-sensical or offensive wordings).</p>

<p>It's a protection for us. If a new user wants a retag, they can simply ask so in a comment. Any regular user will add the tag. </p>
 27: <p>It's a bad idea, simply because a new user doesn't know how the system works. He doesn't know what is the accepted format for tags in Stack Exchange in general.</p>

<p>Even a user who's active on another site (And thus gets a 100 point bonus), doesn't know what the accepted tag scheme on <em>this specific</em> site is.</p>

<p>If a user wants a question tagged with a specific anime which doesn't exist, the expected behavior is:</p>

<ul>
<li>Find a tag which closely matches what he wants</li>
<li>Either wait for a retag by a high-rep user.</li>
<li>Even better, flag the question for retagging by a moderator.</li>
</ul>

<p>I understand the system is problematic, but allowing new users to arbitrarily add tags induces more problems than it would solve.</p>
