Using tab as a keyboard shortcut to hit reply would be very helpful -- personally, that's my #1 way to save edits on wiki pages.
This does work in Flow entry fields, but the difference between an active Reply button and a non-active button is difficult to see with the naked eye. The same is true of the source/VE toggle in Chrome source view. (Tabbing to the toggle doesn't work at all in Firefox; in Chrome VE it's fine.)
Here are screenshots of the active and non-active Reply and toggle buttons in VE mode and source mode. It's really hard to tell the difference.
@Pginer-WMF, this is probably bigger than Flow because of UI standardization, but is there anything we can do to make the active state easier to see?