add an automatic second trait that negates it, but i think you mean you don't want the trait to show up in the menu.
i've glanced through the xml, i don't have the whole thing mapped out - was waiting for release to do that since i don't have time to constantly redo work every beta update.
perhaps if you added a line, say "sean's personal filter string=keep", in the core file that you could use to filter out the traits you dont want. This should be something that wouldn't affect the core game, and you could use a seperate file to actually do the filteriing.
that way every trait has an line of code that declares a variable, which the core game will promptly ignore.