I think it's a collar for the sheer humiliation factor. [Sounding particularly resentful at the moment, yes.]
[And scratching his neck now, feeling a little sheepish that he let his temper get that up.] A lot of things, I guess. Starting with whatever chemical it apparently did nothing about. It's not the first time something like that happened. [he'd told her about having his condition reversed for just one day. It just seems like the Warden punishes the dumbest things and doesn't give a damn about the important ones.]