To the OP, hmm, I don't know. I can see how word choice could be important, as well as the personality of the person you're directing the comment towards - i.e. knowing them well enough to know whether they'd take said compliment the light you meant it, or not. But then you're back to disregard's point, where ultimately any offense taken by the recipient of the compliment falls on that person, not on the person who actually gave the compliment.
But anyway..an aside, I think I'd actually prefer receiving character compliments, rather than generic ones..I remember years ago when I was trying to make sense of my personality, I had no idea what my strengths were because no one had ever commented on my character. I didn't know WHAT people actually thought of who *I* was - what they perceived, what stood out about me. But yeah...to what other people have mentioned, the downside of that is that you might get a dose of being affirmed on traits you don't like a whole lot yourself, and don't place much value on; but I guess it ultimately provides a different perspective, and you can use that information as you choose; maybe it'll provide the impetus to actually push forth aspects of yourself you would rather other people see. ha.
I don't know if it's related to the OP, but sometimes I'll make it a point to compliment a friend on a trait that I truly believe they have, but don't think they give themselves enough credit for.