Permit submitting reviews without top-level comments #2422

I'm not sure why GitHub has added the required attribute to this comment field, forcing you to add a top-level comment, when you have all the comments in the review to speak for themselves.

Weirdly though, I can't reproduce this for RGH's open PRs. This made me think that it was an repo-specific setting but I went and looked through the repo in question's settings and couldn't find anything.

I then checked in Incognito, without RGH, and can't repro it either

which makes me wonder if it's an RGH feature (that I would hope to disable)?