From the OP:
...but I think it is a losing battle to try to control the behavior of commenters.
From a comment by @ChrisCunningham:
...I plan to delete my own comments after a week or so has passed.
I wonder if comments must really live indefinitely. If folks here want a true Question/Answer format, where these items are labeled as such, what about advertising that comments will be summarized (after some interval) and then deleted automatically? I see comments as a way to help folks fine-tune their questions (or answers), but they so often evolve into miniature, threaded Q&A fora themselves. And sometimes, they become really uninviting for new users.
So, I would propose, as an alternative to allowing mini-answers-in-comments, that comments have a fixed shelf-life, and they be somehow summarized/included in the question (or answer) itself.
[Note: I do not have a plan for how this would be operationalized.]