It's not so much that he's a shitty joker clone, he is basically a guy with a personality disorder who feels smug about knowing shit. If that were enough to get you qualified as a supervillain half of
SLU would be running around in latex suits and planning elaborate capers involving flightless birds and/or wacky-yet-deadly novelty gadgets.
If Riddler posted to
SLU his last line in every post would be "Okay this is the last I have to say on this topic, I'm leaving this thread NOW", 5 minutes before posting again except he'd probably also be running shanti-is-coming.com