I don't understand why 0 and O look nearly identical.
replies(6):
Usually type designers consider the legibility of 3, 6, 8, 9, 0 (particularly 8 and 0) to be more important than between O and 0. But for coders, the ambiguity between O and 0 is a big problem, so a designer would consider that.
An example for pilots: you are heading 180 and radio it as "one zero eight". Even if you immediately correct yourself, it's a problem.