How do you tell if a cheese rind is edible?
So this link and this link suggest that there are 3 kinds of rinds.  Summary below:

Bloomy: Appears white, soft, maybe fuzzy.  Can also be reddish/brownish.  Comes on softer cheeses that have a more custard-like flavor.  Formed by a spray of penicillium candidum before aging.  Edible, but the flavor changes and may taste ammoniated over time (consume so long as it's palatable)

Washed: Color ranges from pinkish red to orange or brown.  Caused by bathing the cheese in some kind of solution, be it a salty brine, beer, brandy, wine or some other alcohol.  Contributes to the flavor in some cheeses, and tastes unpleasant in others.

Natural: Formed by letting the cheese age on its own, drying out and growing whatever molds might be present in the cheese or air.  Tends to have a concentrated flavor of the cheese, but may not be palatable.  Examples: Stilton, Montgomery Cheddar, Parmigiano-Reggiano.  Sometimes comes under a cloth cover.  Should be edible, minus the cloth.

Additionally, there are two other possibilities

No Rind: There should be no guessing here.  You've probably had cheeses with no rind...because they might come in a container.  Ricotta, fresh mozzarella, and creme fraiche come to mind.

Wax/Twig/Cloth: Inedible.  Should be discarded

My personal takeaway from this quick research is that I should learn to distinguish artificial covers (cloth/wax) from rinds.  It seems like those that separate from the cheese will either be an artificial cover or an old rind, both of which are undesirable.

If it's indeed a rind, then I'd taste it, both alone and with the cheese, to determine if it's palatable.  For Parmigiano-Reggiano specifically, I've read that it goes well in soup.  Perhaps this is because it's unpalatable-y hard, but still contains the concentrated flavor.

TLDR: look for cloth/wax.  If none, is it tasty?  Does it feel good in the mouth?