The last time we looked at this, the main technical problem was that there wasn't a native way to pre-edit the commit message before hitting the "Squash & Merge" button, and emulating that capability via a formatted comment misses out on a lot of UI niceties.

So for a first pass, I think a comment from the bot saying "Approved PR ready for merge" and mentioning the committers that left approving reviews would be a good way to go (I know Sanyam had to ping me on a couple of issues because I'd approved them, but switched to doing something else because CI was still running, and then never got back to actually merge them).

Cheers,

Nick.