If I do conda remove foo bar and neither of them are in the current environment then I get an error. However if I do conda remove foo bar and foo is present but bar is not then foo gets removed but there is no error or warning that bar wasn't there and was not removed. I discovered this because I misunderstood the behavior of the --features flag, so it also applies to removing features.

I would suggest that a warning is required as a minimum, and perhaps it should be an error to be "symmetric" with a conda install foo bar where foo exists to be installed but bar does not (which just reports an error, and does not install anything).