I think it's more a question of what's easier on the reader, rather than what a reader can feasibly distinguish. Yes, words like "read", "present", "lead" have

I think it's more a question of what's easier on the reader, rather than what a reader can feasibly distinguish. Yes, words like "read", "present", "lead" have multiple prononunciations, but they have a cost; if half the words you encountered were like that, English would be very hard to read. I find "co-operate" slightly easier to read than "cooperate", at the expense of being slightly longer. These are all minor trade-offs (or is it tradeoffs?) of course; it's not a cut-and-dry (but hopefully not cutanddry) argument as to what to do in any individual case.