a) real pseudonymity
b) no photos/videos
c) no infinite scroll
d) no notifications
e) very specific (mildly speaking) topic range
f) very very good ranking and filtering algo
....
(g) guidelines designed for curiosity and intellectual discussion that are enforced by the moderators. No "real" social media platform has anything similar. (so maybe it's more like a discussion board? LessWrong/old phpbb forums)