> If you're firing an employee, they should have known (almost as long as you've known) that there was some culture mismatch, or that their performance wasn't meeting expectations, or whatever.
>> there was some culture mismatch, or that their performance wasn't meeting expectations
I had trouble reading this: culture, or performance. If their performance was good, but they didn't match the 'culture' then it is arbitrary in the greatest order. If 'culture; is important, as I agree it is but in qualifiable ways, so culture is qualifiable, and if an organization cannot put 'culture; into its performance expections, it is likely doomed or very very young, but likely doomed.
If you're leaving a company, you might not have told the manager that you were interviewing around, but you certainly should have talked to them about being unhappy.
If you're firing an employee, they should have known (almost as long as you've known) that there was some culture mismatch, or that their performance wasn't meeting expectations, or whatever.
There are of course always exceptions, where you think someone is crazy or an asshole, but most people are reasonable and can handle hearing that things aren't great.