i don't think i remember all too many of me being suuper active in them, more just secondhand or even thirdhand or something online :P
i like Touhou (still), but i'm not really part of the fandom/community, i more just do my own thing. same with Vocaloid/UTAU.
though i remembered LittleBigPlanet was... a whole mess, but i never really went online there, i just used the singleplayer campaign lol
i dunno, i just don't really participate in fandoms much.
maybe outside of the weird Reddit/Discord transfem catgirls archetype thing for a while, but i left after it became too insufferable. though it was kinda fun while it lasted.
i dunno really if the transfem catgirl archetype thing was necessarily 'infamous' but it was definitely a target for harassment if any were outside of those safe spaces. and later it kinda imploded on itself, it turned into a huge echo chamber and now it's kinda fragmented too.
r/transfem used to be full of them, so did many nerdy Discord servers, but now it's really hard to find one. i'm a remnant of it, albeit i'm a foxgirl, but still lol.
also several yuri subreddits too, they used to be filled with transfems. i was a lesbian some point in the past, but since then they've completely flipped to just another fetish subreddit.
hmmm... i think maybe Roblox? i'm not really sure, but i did play a bit in it? mostly the disaster survival-type games, but i remembered how much drama would swirl up like a tornado at times :P