I hate that too, but have a tendency to do it myself (usually using it's when I mean its, as you've noticed when proofreading the help files for emplode), so can't make a fuss.

But, my pet hate is the evil, don't-deserve-to-be-using-a-computer types that use feet and inch marks when they should be using curly quotes. And improper use of hyphens, en-dashes and em-dashes.