I strongly agree to have discretion of CancelledError and other general exceptions, though I don't have concrete ideas on good unobtrusive ways to achieve this.

If I write my codes carefully I could control most of cancellation explicitly, but it is still hard to control it in 3rd-party libraries that I depend on. Often they just raise random errors, or CancelledError is swallowed.

Also it would be nice to have some documentation and examples on how to write "cancellation-friendly" coroutine codes.