Or you can just send them a PM or post it somewhere else as long as they get a chance to quote it and put it in their signiture/MMing topic so everyone can see your expression of undying love and devotion for them.
-- I think it should be "undying love and affection", devotion is decent though. Maybe I saw it in a movie.
Player one: Selling membership pin, 1,000,000gp!
Player two: Yeah, okay, Official Middle Man?
Player one: Fine.
Player two: Thanks for Selling Player one, I vouch! Very trustworthy!