[CM30]

Not really a professional career example, but this story reminds me of my time running internet forums, and how I made pretty much the exact same type of mistake a fair amount. I'd take on an active contributor as staff, but end up overlooking their hair trigger temper or hostile behaviour because they'd spent so much time contributing to the site beforehand.

What I didn't realise (and I'm sure a lot of people who keep on these individuals in paid jobs don't realise), is that it starts scaring off other qualified members/employees. By keeping on one bad individual, you drive away your other skilled users or employees.