Tone It Down
The right tone is important. If it's off the music just doesn't sound quite right. And when you're speaking to somebody, the wrong tone can completely twist the meaning of your words.
Speak too softly and you'll be painted as accusing and secretive, too enunciating and you'll be construed as condescending.
True, these assumptions have a lot to do with the context of the physical situation. But just because there is no bodily presence or audible voice doesn't mean that there is no tone on the Web. If anything, it is doubly more important there.