Relevant: I did not actually read the thread before it was deleted.

Even if they're being fed, troll posts are probably going to be below -3, hidden by default. A solution that would not require changing the deletion policy might be for people to stop reading/rehide a post if they know that it's likely to emotionally affect them in a negative way and not serve a useful purpose. (Yes, this would inhibit feedback, but deleting the feedback entirely would do the same, but moreso.)

As a note, I likely won't respond to comments on this -- the topic isn't important enough to me for me to keep up with the discussion; I just wanted to drop in a potentially useful suggestion.