Ah, that’s too bad… must be an artifact of the migration. Can you point me to a migrated topic where spam posts are visible now? Don’t clean it up quite yet – remember I am a plain vanilla user so I can’t see anything that is only visible to staff.
Don’t worry – we’re definitely aware of profile spammers, which started happening en masse around 2015 or so. This is handled in the background by a task that scans for this odd behavior profile (filling out user profile, but not reading anything). This is, again, 100% humans touching actual keys on an actual keyboard. They even set background images for their profile and everything!
There’s additional levels of protection around user profile spammers. We historically told webcrawlers not to index user profiles at all (though that has changed), and new users are limited in both what they can enter in their profile, and what we will display. You’d need to use your browser’s incognito or anonymous mode to view their profile, to see it as a webcrawler would.
There might be a sanity limit of, say 5 or 10 years where topics auto-close… ? I don’t have any particular opinion on this. I’d say it depends how often you get unwanted spam post bumps to old topics, versus natural conversational bumps to old topics.