dsimcha/phobos — comment on commit 36a5a7373c69dc43beb7ee26a615da75fb54b631
File: std/algorithm.d line 7282
By andralex:

"I" can be confused with "l" and "1". "O" and "o" can be confused with "0". That's why "I", "l", "O", and "o" should not be used as symbols.