We get a few spammers on travel.SE - mainly obscure travel companies and travel websites hoping for linkbait, I guess.
However one in particular has created a couple of accounts and posted useless answers a few times, despite suspensions - they start again when the suspensions end. They're suspended again (for longer) at present, but given they started again IMMEDIATELY, I don't see them improving.
Is it possible to block domains, or because you might get someone spamming a site which isn't theirs which would be problematic, block IP addresses? (all their accounts are on the same IP so far).
I envisage problems with banning IP addresses though...for obvious reasons.