This happens all the time. You do some modifications, hit checkin, get told you need to merge beforehand, you do that and it's all automatic and nice and then you hit checkin again and notice the comments are gone.

The comments are of course in the history, but I have had to edit them exactly 0 times after the merge. Would be a nicer user experience if the comment was kept there by default (or at least have an option for doing so).