An XP martyr is the diametric opposite of an XP whore. Someone who forgoes experience for the good of the database. These unsung heroes quietly labour over their factual writeups (or poetry, or personal experiences, or...) always contributing, never pausing to make a dumb joke, or start a getting to know you node.

Of course this expression is a little hyperbolic. No-one ever died for the sake of XP!
Although, Katyana did come awfully close.