I would always give positive comment, but even where criticism is well intended it can be wrongly construed, so I avoid that these days.
I have the attitude that if somebody is held up as some sort of modelling God or worse, acts like one, I'll tear them to bits. If someone is just good in a humble way, I'll praise them from the rooftops and if they are struggling, I'll always help wherever I can. I figure that's the least I can do after so long in the business.
Martin