The key point was wrong wrt Wikipedia :-)
>a forum for free thought
>if it [isn't] policed by content moderators around a set of culture rules
The rules are mostly invisible to us because we are surrounded with, and submersed in, this very culture 24/7.
To get written up in Wikipedia one must first get published in a reliable source. This mostly means a journal or "books published by respected publishing houses" (full list: [1]). The publishing is the gatekeeper here; the wikipedia moderators are a secondary consideration.
This does indeed silence out a priori (i.e., censors) ideas that are culturally unpopular or frowned upon or just held by small number of individuals. To avoid muddling the argument with hot button issues, here's a very mild and barely objectionable example: picoLisp, a modern interpreted programming language with dynamic scoping. Having it written up, and then kept, in Wikipedia is an uphill struggle spanning years, and with sad reversals & losses. And that's with ideas that are only mildly unpopular.
Again, Wikipedia's utility is clear and recognized. Let's just not mix it up with a public square.
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[1] https://en.wikipedia.org/wiki/Wikipedia:Verifiability#What_c...