itch.io

 Maybe discord can get away with it. But on a regular website, if I harrass you with pm, there has to be means of the site removing the messages and banning the account. The harrassed account being able to "block" the offender is just not enough.

Completely understandable from an ethical standpoint, but are they also obliged legally?

Anyway, that problem already exists within the moderation of comment sections and community forum, so essentialy it would just boil down to the question of scale, and with allow lists that should almost be a non-issue (not saying it won't happen, but significantly less frequent),

Yeah, but we already have this with the forums. Should we not have the forums either? There's virtually no difference between the two. Direct messages are not private messages. They're publically shared conversations between two or more users. They're just not made accessible to everyone online by default -- that's the only thing that makes them "private". No private information should ever be entered into these messages -- just as you wouldn't post any private information on the forums.

And if you treat them like that -- with everyone well aware that these are not really private in the full sense -- then what's the high maintenance?

You're not doing anything more than the forums. You're just allowing people to talk to each other directly, as opposed to having to post every conversation between each other for everyone to see out there.