Buddhist forums & communities
My impression is BSE is 5.4 years old and is unrelated to other Buddhist forums.
The first major Buddhist forum I was aware of was called E-Sangha, which was extremely sectarian, and banned lots of folks, including DD. Legend says it was cyber-attacked. Read here.
From the ashes of E-Sangha appeared to arise a number of Buddhist chatsites created by David N. Snyder Ph.D, such as:

dhammawheel.com (Theravada)
zenforuminternational.org (Zen; now defunk)
dharmawheel.net (Mahayana)

Most of the founding members of dhammawheel.com were active on E-Sangha, such as the current admin Retrofuturist and Venerable Dhammanando (and some now ex-DW moderators).
There is also a current chatsite at newbuddhist.com with moderators who were E-Sangha members (however, possibly not the site owner).
Another independent forum is buddhismwithoutboundaries.com, which I and another ex-E-Sangha-bannee posted a lot on.
There is the low traffic Goenka orientated vipassanaforum.net and more low traffic off &amp; on forum called freesangha.com and low traffic secularbuddhism.org/community/
There is dharmaoverground.org, where members focus heavily on personal claims of attainments.
There is discourse.suttacentral.net, which appears to have a narrow doctrinal focus
There is bswa.org/forum/, connected to Ajahn Brahm's monastery.
That's probably it.
Oh... and there is Reddit, which looks like a sectarian free-for-all to me; where folks can set up their own site and cult.
I post/have posted on most of them, under various pseudonyms, unless I am banned or forget them.

Because I'm in the habit of reinterpreting scripture, and questioning traditional authorities, I often find that fundamentalists are upset by what I write. For instance some time ago a chap going by the name of 'Namdrol' on the E-Sangha bulletin board, in a discussion of the Theravāda three lifetimes model of the nidāna chain - for which there is no Pāli Canonical authority - declared: &quot;to reject the three lifetimes model is harming the dharma&quot;. I mentioned back then that I thought this a fundamentalist view, but was told that the word &quot;fundamentalist&quot; was banned in that forum (along with any reference to the New Kadampa Tradition which was a bit of a give away). E-Sangha died not long afterwards, but not before I realised that online forums, and arguing with strangers on the internet generally, were a waste of my time and started focussing on writing this blog.
Jayarava - BSE member