He is treated as a singular character in game, and so can only be stolen once.
There is a minor bug in one of reward dialogues that fails to animate his mouth when he speaks. It is the dialogue where he says "A little something extra; for friendship."
There is a potential bug with the Mage's Collective Liaison in the Denerim Market district. If you have visited Frostback Mountains with the "Notices of Termination" quest but did not talk to Starrick, this can cause a permanent exclamation mark over the Liaison's head. If you have visited the Brecilian Forest but did not re-enter to slay the Cabal then a possible glitch can occur.