I keep forgetting to post about this.

Berserk falls apart when you and your current target are in a sanctuary.

Each round of berserk, you still drain the usual 10 stamina, but nothing else happens. There's no messaging of any sort, and no way to tell what's going on unless you see your stamina drain and/or try to take any action.

Because you cannot start a berserk in a sanctuary, and because creatures generally do not wander into sanctuaries, this is not the most common occurrence, but it can happen. Other players sancting/singing Peace while you're there and fighting is the more obvious one. The far more common one in my experience is when you're berserking with creatures that raise the dead and sanct the room in the process (Ithzir Seers and Mintoaur Magi, but not the Wyneb dogmatists - they don't sanct).

The first time it happened to me, it took me a good 15-20 seconds to figure out what was going on.

When this happens, I would expect one of a few things to happen, in decreasing order of likeliness:

1: Targets in the room are invalidated as if dead, and the warrior looks for targets in the surrounding room to chase after on the next Berserk round. If no targets exist, Berserk ends.
2: Berserk ends automatically at the beginning of the next Berserk round, since a Berserk state cannot be sustained in the peace of a sanctuary.
3: As things are currently: you waste stamina as the Berserk rounds pass, but you at least get a message saying you can't bring yourself to strike.
4: Some Berserk formula is substituted for the sorcerer stuff in the sanct breaking calculation: success, chase as per outcome 1. Failure, end berserk as per outcome 2.
5: Treat sanct like stun, etc. Some Berserk formula is substituted in the sanct breaking formula, success: your will to fight is so incredibly deep as to overwhelm the spirits of peace, break the sanct and continue berserking. Failure: wasted round as per outcome 3/failing to break a stun.

#5 seems like the most fun to me, but also the least likely. If you really want to get into it, let a warrior enter berserk in a sanct if he/she is holding a sanct-breaking crystal.

But at least throw a message in there to make it obvious what's going on.