@driazati Hi
As we discussed today on TVM Community Meeting, the second part of your proposal about taking the final commit message from the PR’s body, in my view, is a prerequisite for the Commit Message Guideline we’re discussing.
It seems the community likes / uses / is used to the additional commits (i.e. commits pushed to the branch AFTER/on top of the initial commit(s) used to create the PR, usually created as a consequence of the review process, when reviewers / maintainers request changes), which is fair, but because of Github’s squash-and-merge mechanism there is no way to land a good commit message since the additional commits will anyways get squashed and merged into the final commit message, ruining to a large extent the essence of the Commit Message Guideline (not even using the fixup! tag to make a linter, e.g. Gitlint, ignore the additional commits messages won’t help because Github will ignore them anyways).
Hence, thumb up from my side 
Btw @areusch raised a good point that changing the PR’s body will re-trigger the CI, but if I got it right there is probably way to set it off so if the author wants to do a last minute change in the PR’s body message (after the PR is reviewed and the CI is already green) that’s not a big deal (e.g. CI won’t re-trigger)?