Picked up a block of manchego for the first time, and tried to eat the thin rind which I assumed was an edible wax with dye. NOPE NOPE whatever it is the taste was very much of the non-edible variety, chemically and strongly bitter when the cheese is very mild.
But in another case with brie I wasn’t sure what the rind was or if it was edible, but I liked the taste and found out it is eaten in France.
Aside from cases where the rind is obviously plastic of course.
That nasty taste was probably natamycin, which is used for preservation of hard cheeses. As a rule of thumb, if you can peel off the rind or it reads “preserved with E 235” on the package, you shouldn’t only peel but cut it off ca. five millimeters deep, because natamycin sinks into the cheese and that stuff is also antibiotic. When in doubt, you should ask your cheese monger. The rinds of soft cheeses, like your brie, are usually edible unless you’re pregnant, elderly or have an otherwise compromised immune system.
…and it’s the whole of the soft cheese that you’re not supposed to eat, not just the rind, isn’t it? At least, I’d definitely remember if I’d been given a dispensation to eat yummy Brie insides while pregnant.
Anyway, I think the difference is that soft cheese crusts are just made out of cheese, like the rest of it - just hardened due to exposure to air.
Aspidistra, maybe the precautions differ from country to country. In Europe, pregnant women are advised not to eat any cheese or dairy product made from raw milk or to cut off the rinds of soft cheeses made from pasteurized milk because these may harbour nasty bacteria (let’s face it, it’s mold).
But since it’s easy to contaminate the insides of your brie when cutting off the rinds I can see why doctors think “better safe than sorry” when they declare any moldy cheese verboten.
I save rinds from parmesan or romano cheeses to put in soup.
Yes, here the advice is just “don’t eat soft cheese”
However, the prevailing advice climate for pregnant women seems to tend towards “if we didn’t prove it’s 100% safe then DO NOT EAT OR YOU WILL KILL YOUR BEBEEZ !!11!” I’m quite open to hearing that soft cheese insides are actually IRL perfectly fine.
The white rind on soft cheeses such as Brie, Camembert, etc is formed from mould. It’s edible (and IMO, the best bit of the cheese). The rind on harder cheeses is formed from drying, often with the assistance of moulds (Stilton, for example).
Cheese mites also play a part in the formation of rinds - anything that has a powdery rind (Mimolette, for example) probably has a thriving community of cheese mites living on it.
It’s all edible as long as you find it palatable. The things that are not edible are things that are not actually rind (waxes, plastics, leaves, bark)
I just grate the rind of parmesan like the rest of it when I’m making a carbonara.
Aha! So even Mangetout has his limits! 
From an earlier thread:
Also some cheeses, like English farmhouse cheddars, are wrapped in cloth. You can’t eat that.