I like the redesign overall but one issue that I have found is that, because I am An Old™, in the desktop breakpoint my normal behavior is to craft my response and then press tab and enter to submit the post. This worked accurately in the old version but this experience has the Markdown editor button as the element that takes focus if you tab out of the div that behaves as a textarea.
This has effectively broken keyboard navigation because I either need to press tab five times or use the mouse. Can this behavior be updated so that the Reply button takes focus on tab out of the compose textarea? I would argue that a large majority of users simply want to post their reply rather than use any of the formatting options on a regular basis.