He banned Runescape, because Jadex complained about people hacking accounts and bragging on Hack Forums, so he banned selling of Runescape accounts and removed the whole section. After that, a lot of people started to scam for Runescape items and he had to ban the whole Runescape discussions.
I think not many people on Hack Forums play Habbo and there are less threads for it, not much spam and that's the reason why he didn't ban it probably.