[claudiawerner]

4chan has an extensive list of rules; only the /b/ (Random) board is exempt from most of them - with the caveat, they say, that the moderators of that board are also exempt from abiding by the rules of who to ban and for what reason.

Even on /b/, doxxing, calls to raid other boards, complaining about the moderators/admins, submitting false post reports, impersonating admins, etc. is banned. On all other boards, even seemingly innocuous things like anthropomorphic (furry) imagery or even posting images of characters from the show My Little Pony (other than in the /mlp/ and /b/ boards) is disallowed.

Porn is disallowed on the majority of boards, and even risque images are sometimes removed; the rules are enforced to the degree where a SFW board (e.g. /jp/) can have threads about Japanese porn actresses, but you're not even allowed to post a nude.

4chan is quite heavily moderated and there is a whole team of janitors and moderators for all boards that respond to reports behind the scenes; you only rarely see them chime in like dang does on HN. For a while, even "share a screenshot of your desktop" threads were routinely being removed from the /g/ (Technology) board by janitors.

As for Gab, I recall they even ban softcore/suggestive pornography or imagery. It's certainly not the wild west just because its users are more sympathetic to the first amendment.