Suggestion: move region left/right *by semantic unit*?

[XZF0]

... probably depending on the mode. E.g. if a sentence is selected in text mode, it makes sense to be able to move it to before the preceding, or to after the following, sentence.

This does blur the boundary between left/right and up/down. Related, but more like before/after.

Semantic units in the sense of https://github.com/magnars/expand-region.el