As reported here
https://forum.cockos.com/showthread.php?t=260552, when I (foolishly, maybe

) apply "Reverse item as new take" to a video item, Reaper tells me that it cannot reverse a MIDI item, and then opens the external MIDI editor.
This is highly unexpected, and a bit annoying.
What I expect is that Reaper tells me that it cannot reverse a video item, and that's it.