Howdy! Yep I'm aware of all of that. I'm sorry for perhaps not being clear enough in my original comment.

You allude to a problem by suggesting blocking u*, these accounts can be created when the old one is blocked. Even subscriber accounts can be created at will & higher cost, though are likely less of an issue.

There is a problem that irc.example.net can't say "These users all seem to be originating from this single open proxy, lets block it." They need irccloud to do that.