Thanks for this. Just now I had a bunch of comments go through just fine, and then I went to the next page of comments and zap -- right back into the same problem. (That's happened more than once, btw. Is it possible for going from page 1 to page 2 in the inbox to mess something up?)

But I'll keep you posted. At least I'm not getting 502 error messages at this point -- I had a mess of those earlier today.

I probably should have mentioned also that I have an open support ticket, #46454.