Comment by bryondowd

Makes sense that a cockpit wouldn't need a clear distinction between brackets and parenthesis, or |. But I am surprised about the similarity of 0 and O. I recall when I went to the ATC academy they really drilled in using a horizontal slash through zeros when hand-written. Also had to underline the letter S in any case where it could be ambiguous with the number 5 (as in a plane's tail number). I think we also had to put a horizontal strike through the letter Z to distinguish it from a 2.