if you didn't just say that, nobody would have known. now they know. but otherwise no it's not against the rules
It's not against the rules, it is an unconscionable act, however. You probably wouldn't be banned or anything like that, because... it just wouldn't matter. If the person got famous, scammed, etc, then... withholding that information... I could see you getting banned for that . Honestly, though, they can't ban you for not telling... even though you should... they can't require you to put yourself at risk by revealing said information.
So basically according to everyone who's not a Mod, it's not against the rules. All the mods say it is against the rules. Lol
It's not allowed to be allowed because being allowed would mean it's not allowed to be allowed, allowing it to be allowed by non-allowers.
If you're blatantly withholding information, then of course action will be taken and it's highly likely you will be punished - as essentially you're assisting another member to ban evade.
You would say Ducel would know how to handle this Considering ducel has "Got scammed? Want your money back? CALL DUCEL. Professional scam detector, small fee of 500$ with scams over 15$. Call now and get 5% off every time you get scammed!" in his signature.