This feature might already exist in the code somewhere, but it’s probably worth mentioning as an admin feature.
Over the years on the old HTG forum, we’ve noticed that the same exact spammers come back and manually spam the same links, over and over and over. We’ve also been hit by automatic bots a few times, though I’m less worried about that with Discourse. It’s really the manual spam that’s just tedious and consistent.
It would be useful to have a URL blacklist for spammers. Possible ideas for discussion:
Automatically hide and flag posts that have a blacklisted URL, so moderators can check for actual users posting the link for some unknown reason.
Automatic and temporary ban if the link appears in the user’s first post or they post the same blacklisted link more than once. Flag alerts the moderators, or not.
The real goal, of course, is to prevent spammers from wasting people’s time, especially the moderators.