I think that the most profitable action is your first suggestion -- don't feed the trolls. The second idea is understandable, but not really quantifiable. The persons moderating the consideration presumably always try to see if there is value/reason to reap in the considered node -- that's why they're experienced monks with this power. One of those nodes had 12 keeps and 11 reaps, which would indicate that a lot of people felt it unnecessary to delete.
The IP address thing is a blunt sword, as you say, and provides information that most moderators won't even use, IMHO. Maybe the IP could be recorded in the DB and if a large number of nodes from one IP are considered/reaped in a short time, the janitors are notified to look into the situation. But that does expand the db considerably. Is the problem bad enough to require this?