I think there is a way to circumvent a suspension. I don't know if it's a bug or by design. A week ago on Travel.SE, a user was suspended for 90 days, and thereupon he decided to delete his account on Travel.SE.
Yesterday the same user signed up again on Travel.SE, and all his questions, answers, reputation and almost all badges were restored; only the votes and review audits were not restored, and...he wasn't suspended anymore. I informed our moderators, and he was suspended again, but on a site with many more users like Stack Overflow or Super User, it's almost impossible to check that.