When you play kalimba, you should always be willing to accent special melody notes, and let the other support notes come in at a lower volume. Why is this important?
Not always, but often, melody notes will be fairly high in an instrument's range, and accompaniment notes will occur in the middle or at the low end. A guitar has a three and a half-octave range. The piano has a seven-octave range. On both of these instruments, you have a big difference in the pitch of the melody and accompaniment notes, resulting in the melody and accompaniment parts being easily distinguishable by the ear.
And what about on the kalimba?