Well, sure, but what I’m saying is that literally 9 out of 11 examples of good changeset comments follow roughly (or exactly) that form, possibly with the source added. So when both a large amount (majority?) of existing useful comments as well as the documentation follow that form, and that form could (presumably) be generated, why shouldn’t we provide that generation to mappers?
Sure, no tool will be able to provide the why as in “added buildings I found during a bike ride through the town”, but it should be achievable to generate “added buildings based on a survey” (based on the contents of the changeset and the source= tag). We can still encourage people to write more (and maybe some even will who don’t today, having been freed from specifying “what”/“where”/source in their comment), but I actually think this might improve the overall quality of the comments.