On some controllers, like the old Fanucs, any time you change cutter comp, you have to put an intermediate point in there simply to "resolve" the comp.
When you're coming off of something, it's no big deal because, of course, the cutter isn't in contact.
But when you're going onto something, you need to turn it on; approach the part to a point not in contact, thus giving it a spot to introduce the comp; then start cutting.
Turning it on and off is no big deal, just gotta put in an extra point or two that you don't care about. On a controller that might not be smart enough, turning it on and off will result in a 'taper' as it moves to the comp position on the NEXT point. This can be a real frustration if you don't expect it (I know).
Equally inconvenient are some of the newer controllers that read the comp and move exactly then. This can result in gouging if it's in an inconvenient spot.
I don't recall a time i've switched from RH to LH (G42 to G41) comp, only to and from LH and cancel (G41 and G40).
Myself, i'd just input it as another block. No big deal. Just cancel (G40) each time. That way there's no chance of any lingering data stuck in some register somewhere that could create a mystery problem sometime down the road. But i'm generally extra careful like that, anyway.