A few related things here, let me know if they need breaking out:
I can’t figure out how to tab to the Category dropdown. I expect it to come after the title, but tabbing from the title goes directly to the post body.
Tabbing from the post body goes…somewhere. I’m not sure where. Wherever it is, it needs a focus style. Tabbing a few more times takes me to more mystery places which I can’t locate because they don’t have focus styles.
It would also be nice if Cmd-Return / Ctrl-Enter from the post body was “Create Topic”/“Reply”. That’s become pretty conventional: Gmail and GitHub both use it.