As has beed discussed in Considerations for editing and approving edits for closed posts, editing off-topic posts to improve them is counterproductive.
Recently I've been reviewing this edit: https://aviation.stackexchange.com/review/suggested-edits/52417
This question isn't about aviation or anything related at all - it doesn't belong on the site in any way. At the time it was flagged, but not closed. Editing it doesn't really add value, as it's just going to be closed/deleted. The edit was an improvement, but 0 times N is still 0.
As it happens, the edit got approved, which put the question back into the review queue.
So, to the community: should we approve or reject edits to non-salvageable questions?
What should be the reason given for rejections? I used "harmful", which looks too harsh, but it's the only option with an explanation field attached. Possibly it should even be a separate rejection reason.