I do a lot of eBook and print book formatting for Nepo Press. Because of this, I suppose, I am particularly sensitive to needless formatting and proofreading errors and do all I can to eliminate them.
I think I have found a nearly perfect method for proofreading. The trick is this: if even a single error is detected, another full proofreading must be done. Simple, easy to understand, but nearly impossible to do in practice.