What is the character display length of the handle accompanying one's icon?

When my icon displays in tribe postings, my handle ("Charmaine") is truncated to display only 4 characters ("Char...").

Such truncation is not consistent among icons, I've noticed. One person's icon may display a 7 character handle, while another person may only display 5 characters.

What's the deal with this truncation issue? And is there anything I can do to expand the handle character length currently displayed when I post to tribe?