I'm not sure where else to post this, and I don't have much experience with Sonic's grind (since I assumed it was bad news). But it turns out you can SD during a grind. This includes B-reversed SD. It's strange because you can't spring, homing attack, or SC... but the forward input seems to cancel the grind even if it comes slightly after tapping B, which on its own doesn't work.
Similarly, you can't shield during a grind, but you can dodge-roll!
I'm assuming this is known, but it wasn't known
to me, and I don't know where else this type of stuff would be discussed... lulz.
Anyway, because of this I'm starting to really like grinding! I just dash around the stage, haphazardly swinging the control stick from down-right to down-left, for anything from runs/slow-runs/foxtrots/grinds/dash-dancing; the more the faster the merrier, just so Sonic looks completely frickin' ******** (and unpredictable) moving around the stage.

Mixed up with SD's (both directions, B-reversed and not), Sonic's a total spaz.