Okay, I'm finally slowing the influx of users and spam posts just by automatically marking people that use certain email domains as spammers.
Funnily enough, they don't seem to be noticing their posts are being blocked -- I'm returning a post ID that leads to a page that mercilessly trolls them for spamming the system, but they're not seeing it.
Anyway I'm pretty happy about this, as it's saving a lot of database space from being consumed with junk.
Some of these changes also involved improvements to the admin interface for deleting problematic users. (It always blows my mind that Mastodon doesn't allow this, but) the self-hosted version of Write.as will now include these kind of admin controls for users.
