Thanks for the tailgate open/close research. I agree with your assessment that frequent manual use could damage the electric drive motor. Occasional use, not so much. It's my opinion that Honda prefers opening and closing to be done electrically, with manual use for emergencies, etc.Asked the dealer the question on the rear tailgate yesterday.
It is "recommended" that you open and close the door electronically versus manually. I couldn't get an answer if prolonged manual opening or closing will cause a problem though.
Kind of a lame answer I know.
My take. There's a fair amount of resistance when you try to open or close manually. I'd say that its likely if you open close manually over time there would be damage or loss of efficiency. That being said once and awhile likely not.
I went through the settings this morning and didn't really look, but it may be possible to deactivate the power feature on the tailgate too. I'll check again at some point.