Preliminary thinking says…
Look at this thread:
Scroll down. Things like that don't happen often but are a consequence of lack of Reddit's "show more comments" stopper on comment trees. I'm not saying that your proposal or line of thinking is wrong – in fact, it sounds like a good idea – but this is a kind of edge case that needs to be taken into account. Either by throttling the length of comment trees or some designer magic.
I want to stress that those are only nit-picks. It's a very good style. Readable and IMO feeling appropriate for the site. Unfortunately, the only way for me to help is to break it. ;)