Any advice? I'm really trying not to show bias toward Patches, and right now I'm planning on trying to nip this in the bud with the Curse the Gypsies put on him. Every time he tells a lie, the DC to resist the Curse's effect increases by 1. When he fails the check, the DC resets to 10 plus the number of times the DC has been reset.

Eventually, if Patches keeps his antics up, he's going to render his entire skillset useless and be pathologically afraid of lying. He's not yet aware of the curse to the point of taking me aside and commenting that he didn't understand why his character would just blurt something like that out, but I told him that he has no idea why he did it either. He's just suddenly got this compulsion to say what's on his mind that he's struggling with.

Even if he somehow manages to break the curse by accident, I think I'm going to keep SMSing him for saves as a gentle reminder.

I don't want to deal with this OOC. I don't want to reinforce negative behavior either, but I don't want to control my PCs completely. I agree with Patches' PC, that my Cleric's kind of RPing a twat, and that Patches would in fact completely get off on taking him down a peg or two. I will also give him credit that he also discarded the Knight's weapon despite the fact that they are really close IRL, so he's definitely not personally taking anything out on the party.

You think the Curse will be enough to put Patches back in line? I'm not sure what else I can really do. I'm going to start giving everybody but the Knight a +5 to sense motive against Patches after his slip-up for the next session or two due to Patches making himself conspicuous. This should almost ensure the Loremaster and Cleric a really good shot at seeing through his min-maxed bluff skill.