I don’t see why my answer would change based on who I was playing with, I mean, a -12 to Coercion doesn’t necessarily mean combat will result, it just means that person can’t EVER get anyone to do what they want for any reason. If they’re trying to get someone to cooperate, or like them, or whatever, they just won’t be able to. I assume that’s what the player wants if they make a character like that. I would also encourage the other players to portray their characters as laughing off whatever suggestion they give. Even if it’s a very good one. After all, what could someone like THAT know?

Corley, I would never encourage my players to do that to another player for picking those drawbacks, especially if the player is new to RP. The golden rule in RP is Respect. As a longtime RPer, not every suggestion from a player who had incorporated this drawback has to be forced to do a persuasion check and then a coercion check to make a point. If the argument that flawed character is making sense, he doesn’t need to make a roll for it and if the other player(s) want to support or even change their stance, then it’s their prerogative. I’m not saying that players can’t handle distinguishing IC denigration from OOC denigration, ie. taking the RP personally but from experience, new RPers have more of a tendency to do that, especially in the presence of strangers.

If it’s a well-experienced RPer who is in a group that they know well and knows what he’s getting into and wants to RP that, then yes, it’s his prerogative but as my job as GM, I would still want to let the character rarely be able to feel respected so that the player’s enjoyment of RPing that character doesn’t diminish. It’s a GM’s job to help keep their players motivated to keep RP that character.

Whether experienced or not, I think you should tell the player what they can expect from having a Coercion penalty so high. Then they enthusiastically say, “Yes, that’s exactly it! I want my guy to be an absolute disaster when it comes to trying to persuade people.” And I would expect them to roleplay being bad at it with other PCs as well.

Well, that’s the beauty of an initial player interview. One of its purposes is to talk with the player about the drawbacks and abilities that could be roleplayed by their character. It’s their choice to take the penalty but I wouldn’t play to it to penalize that player all the time. You’d find a way to focus on the characters’ strengths when writing such scenarios afterall.