Discussion of Gamergate has been taken down in some form from every major communications platform other than (to my limited knowledge) 8chan and twitter. Facebook, Reddit, YouTube and 4chan have all removed content related to GamerGate
I would state this slightly differently: discussion considered to be abusive by the moderators/admins of their sites has been taken down in some form from every major communications platform. In some cases, that discussion involves GamerGate.
It is possible to construct a conspiracy theory in which GamerGate is being censored, but given the existence of (say) http://www.reddit.com/r/KotakuInAction/, it's hard for me to believe that Reddit as an entity is removing all GamerGate discussion.
Also to fuel the conspiracy theory we have a recent ABC Nightline piece[0] which has 28,404 downvotes and 1,028 upvotes about the contentious issue. Also heavily censored comments where some of the removed comments only criticize the content of it and don't attack any specific persons in it. While comments like "4:05 That is nightmare fuel. How is it possible for a person to look so grotesque?" still aren't censored.
In no way am I stating an opinion, just adding something I observed to your comment:
For about a day, comments anywhere on Reddit matching `[zZ]o[eë] ?[qQ]uinn` resulted in what appeared to be an automatic global shadowban. I verified this by asking "who is Zoe Quinn?" on a throwaway. When people say totally nonpermitted discussion they might mean something like that.
Not really. Perfectly polite non-offensive discussions of GamerGate and related topics were removed. Also completely polite dissent in comments from under multiple articles (on guardian and verge for example). KotakuInAction was only reddit thread allowed to stay - and was not allowed to mention gamergate initially.
Deletion comment of widely popular reviewer who screen-capped it and then tweeted to his followers was head scratching moment. Same happened to british journalist who was harassed in relation to the controversy. She commented under guardian article and her comment was deleted. She was kinda angry afterwards.
The existence of KiA doesn't prove that GG isn't being censored. It's containment, you can't talk about GG in any normal subreddit like /r/games or /r/gaming.
That and KiA was recently threatened a ban from the admins for their boycott campaigns against companies. Admins have said that you cannot link to a public representative of a company as it would constitute doxing.
It appears that the classification of any discussion at all, short of total condemnation was considered by many places to be "abusive". I have never in my life seen such aggressive comment-filtering, almost everywhere, as related to this topic.
It is a reaction to "sea lioning" where GG seems to be injected into every possible discussion and once flagged as off topic and removed the conspiracy theory of "censorship" is fueled.
Talking about GamerGate on any forum will get you the craziest vote brigading you've ever seen. My original post went from 8 upvotes to -1 in less than a day.
God forbid you use the hashtag on Twitter. It's like summoning demons from all sides of the argument.