I always thought it was idiotic that one you got lvl 60 you couldn’t disable xp gain. I would like to be able to do all the quests on one character. Once you hit level cap the quests become so stupidly easy I can’t bring myself to do them. There is no good reason why this isn’t available.
It almost certainly is restricted due to PvP twinking. A player halts their XP, gets the best gear/powers available, then enters PvP (probably Battlegrounds) against other players that are trying to level. A similar issue might arise with Warmode.
Damn, you maybe right. I hate PvP so it never crosses my mind