Ignore /b/, /pol/, r9k and all the weeb stuff and you can find some properly good communities which remind me of the old internet. /sci/, /mu/, /biz/ and /fit/ can all have their moments from time to time.
I vaguely remember a poster having digitised his entire niche Serbian breakfast cartoon collection
A lot falls through the rather wide cracks in legal distribution methods
Good luck doing that on 4chan
Go away
Until then you can use some 4chan boards if you ignore all the weeb shit.
When I tweeted about it, I said “The best known lower bound for the minimal length of superpermutations was proved by an anonymous user of a wiki mainly devoted to anime.”, by which I meant Wikia (which was pretty anime-centric at the time).
I think, combined with the fact that the problem was posed to 4chan in terms of Haruhi, and because it makes a funnier story, that the anime angle has been a bit exaggerated.
Having said that, the author of the proof is not (to the best of my knowledge) a mathematician, nor does he have any apparent desire to publish his result in a conventional form, so it's still a pretty unexpected place for such a result to originate.
>by an anonymous user of a wiki mainly devoted to anime.”, by which I meant Wikia (which was pretty anime-centric at the time).
The Wikia in question is the official 4chan /sci/ Wikia.
4chan dates back from a time where you'd have, say, forums for people who like X, and that forum might also have off-topic boards for stuff like food, travel, politics, and other off-topic discussion. While there are people who are interested in specific topics in said boards, everyone on the site across all boards are expected to like X.
As 4chan is wide open and due to the existence of /b/, there is thus a constant flow of people who aren't anime fans whinging about anime in the non-anime boards, who are generally ignored or rebuked.
I haven't been a regular visitor for some years, so some cultural loss might be expected, but certainly at the time that this happened, 4chan was still solidly an anime community.
Here are a few examples (which also demonstrate that while it's hard to define 4chan users in any way simply because it's an undefined set of random people that might visit and leave at any time, the only commonality would that most (not all; the so-call "redditors"/"tourists") are anime fans:
https://4archive.org/board/qa/thread/382065/whats-the-deal-w...
https://4archive.org/board/qa/thread/564357/its-acceptable-t...
This is apparently an archive of the original post:
http://4watch.org/superstring/
It's a question to a math community, using an anime meme template and referencing another anime. The discussion is very much not some anime fans having fun with a silly question, not knowing they are dealing with frontiers of math. Instead it is math enthusiast having a go at what they know is a difficult problem. One even links to a stackexchange question, stating that this is an open problem, and the poster of the link says that if they solve it, they should post it to arxiv.