Will this rotate on the bb and go into the chain and chainring?

mine has never moved since fitted.

Not if you A) de-grease the contact area, and B ) tighten it up enough

Mine did to start with. I have now put a little bit of locktight on the drive side BB before assembly. Been fine since.

Thats a good idea, glue and possibly give the surface a key.

Mine only moves when I clobber it with a rock, unfortunately this happens surprisingly frequently and is mighty annoying as the chain then gets pinched on the stay.

Mine’s never moved, even when I’ve whacked it with a hammer!

Depends how tight you do it up.

The downside of doing it up real tight, is that if you do eventually manage to move it, you can’t easily move it back! I keep mine ever so slightly looser, it still doesn’t move often but when it does I can get it back in place without needing a BB tool.

Mine only moves when I clobber it with a rock, unfortunately this happens surprisingly frequently and is mighty annoying as the chain then gets pinched on the stay.

some people see this is a benefit, as opposed to having the tabs (ie. part of your frame) damaged when an ISCG-mounted guide hits a rock…

I assume this is only an issue when you’re running without a bash guard.. I have an e13 bash and the stinger roller just touches, it shouldn’t be able to move in that scenario.