The ideal tab order in the Reply tool, if the Advanced bar is open, is that pressing Tab once takes the cursor from the body of the reply to the Edit summary field.

It's nice to be able to tab to everything, but in practice, I'm most likely to be tabbing to the Edit summary (if I have the Advanced bar open) and the blue button for posting.

First reported by @Thryduulf in https://en.wikipedia.org/w/index.php?title=Wikipedia_talk:Talk_pages_project&diff=1009493153&oldid=1009492389