Did you ever hear someone singing to themselves, think their voice absolutely angelic, and comment to them thusly? I'm always suprised by how often people deflect this type of complement away with replys like '...not really' or 'i wish'; sometimes they'll just get red, stop singing and change the subject.
It's ok. Not everyone knows how to take a complement. But I believe we're here on this earth to encourage others and to build each other up. Regardless of how they respond (or don't respond).
Let's say nice things to others, period. Let's help people feel good about themselves, eh?