Because the priest character in WLK can't use one handed sword, I bought the wrong equipment for my priest character, Bloodsurge, kel'thuzad's blade of agony (LVL 284), now i applied for returning it to coin, and bought a one handed hammer again. My character name is Pgdeliverer in icecrown.
I have not bought or got any item from store for a long time now and my button is there. Just for info : )
The button is there by default for everyone, but the list of items to choose from will be empty if there's nothing applicable to ask for one.
If he was banned from using Support he would have a message stating that instead of the option just being empty. You either have access to Support Tickets or you don't, it's an all or nothing, no "banned from item misbuy only."