Yeah I saw that message from Red Five in the Shed. FLU doesn't really make any effort to hide it and I'm pretty sure he knows we know.
I agree with your overall premise on previously banned members. Obviously there will always be exceptions and FLU might be one. He's annoying, but he also hasn't explicitly broken any board guidelines recently, so I'm kind of torn on his membership.
I cautiously lean towards allowing him to stay, however, I would absolutely be open to a short term suspension the next time he posts something to just to aggravate people. Or, if he posts one of those "I've been saying X all the way back since Y" comments. Those Captain Hindsight, rear-view mirror posts he's so fond of sharing are the primary reason he's been pissing people off lately. I don't think a suspension will curb his behavior, but, it would send a message. And it would also give us an easy reason to permaban him if he continued to act that way after the suspension.