[zozbot234]

> Your site admin shouldn't be the one deciding who you can DM, or which people can follow your feed.

That's a necessary affordance, given the technology. A mail server could indeed refuse to forward some of your emails, and this could even make some sense e.g. as part of spam prevention policy.

[dane-pgp]

There is certainly an argument for preventing unsolicited messages being received from unknown users, but rarely do people value a spam filter which prevents them from sending messages to people. (I suppose there are some corporate filters which try to prevent accidental sending of sensitive information to unauthorised recipients, but that's not the "feature" we are talking about here).

It is perfectly reasonable for a user to want to DM someone on an instance that has different moderation policies from their own, and it is equally reasonable to want to receive replies to those DMs.

If the specifications or implementations don't allow that, then I suppose it has to be justified by saying that the DMs could be used for sharing copyright infringing material (or worse), and admins don't want to run the legal risk of hosting that on their servers. Legally, though, that doesn't seem any different to operating a mail server, which don't typically have Content ID matching systems on them. Perhaps the implementation of end-to-end encrypted DMs would assuage some of these concerns a little.