PR veteran Jeoff Barraclough has this thing he says about how you say things.
"He's a nice guy," Jeoff would say about nobody in particular, "he's not stuck up at all."
What do you know, everyone starts suspecting that whoever-it-is is actually stuck up. Jeoff's point was that, even if you're negating a negative (e.g. not stuck up), the first negative remains. It stands out. It kind of smells.
I should've learnt that when Jeoff told me that oh, years ago. But no, I had to make my own special mistake, on this very blog in fact (there might be a prize if you can find it).
I complimented someone by saying what they were not. And sure enough, the inferred suggestion was that they actually were what they're not.
Lesson - really do emphasise the positive, especially about the people you work with. Our words have meanings beyond what we're using them for. And some keywords - especially negative ones - just stick out like a sore thumb.