The effect of habitual contexts on tone

Sounds complicated, but all I actually mean is that for a long time I've used IRC, IM, and email to talk mainly with friends and colleagues rather than students, because my students generally have preferred to talk with me in class. But, this term I have to communicate with my first year mostly through email, IM, etc. and I find that I've grown so accustomed to being in friend/colleague mode that I continue in that tone with my first-year students. Hopefully this will be ok...last fall I was pretty friendly with some of them and late in the term I had to give a rather stern talk about how my liking them would not stop me from giving them a bad grade, I would just feel worse about it.

But maybe I'm worrying for nothing. Or about the wrong thing. Maybe the one who really causes trouble will be the colleague who has registered so he can see what I'm doing in there... ;-)