Talking to the group out of character is probably a better approach for what you want.
As I understand it, you, out of character, are getting annoyed by something that the other player is doing in character. You are trying to take an in character approach to solving it.
But the problem is that the other player may reasonably think you are just taking a role playing stance. That this is part of exploring the reactions and implications to his character's condition. If so, he may find it a reasonable reaction, simply react in character, probably with some statement of "I can't control it, I wish I could." And the thing is that this is probably a valid in character reaction. But it doesn't solve your problem of being annoyed by the behavior.
Instead of taking in character actions and expecting the other player to take that as subtle signals of your out-of-character feelings, talk with the group about your feelings and how to make the game more enjoyable for you, in a non-confrontational way. Assuming the group is reasonable, this will result in one of two things. Either they will come to some sort of agreement as a group about how to pause this behavior for now such as finding a reliable way to suppress or you as a group will decide that this is still a central part of the game for the group. Either way, you will at least have an open and frank resolution out-of-character rather than trying to solve a largely out-of-character problem by in-character hints.
Incidentally, as part of the discussion, it may be helpful to respectfully bring up "my guy syndrome". To over-summarize the contents of the link, Players should not use "its what my guy would do" as a justification for doing something that is harming the fun of others at the table.