I think your basic premise is wrong Happy Puppy. I don't think it is a characteristic of Fe that it is "marked by calmness and maintaining a happy outward, teamwork focused attitude with a minimum of negativity". That sounds much more like Fi to me. Fe is intrinsically more likely to make emotions known, whether positive or negative.
That's not to say that everything is fine and dandy with your colleague, and that you shouldn't be concerned about him. But if you're only basing this on him acting differently to how MBTI tells you he should, then I think you're making a mistake.
Spamter, I think it's really nice of you that you avoid loved ones when you're in a bad mood. Although I don't think expressing your moods, bad ones included, is necessarily a bad thing. My earlier comment was more about feeler types that habitually use you to dump their bad emotions so that they can feel better, rather than thinker types who blow off every once in a while.