I must ruefully admit to being someone whose fingers (without direction from any higher brain function) type a random homonym at every opportunity. I’ll catch them all when I carefully proofread, but, since there aren’t enough hours in a day, my emails generally convey the clear impression that I’m a complete illiterate! :)

I wonder if “should of” and “could of” might be typos that would stand out even more for someone with English as a second language, since the error has more to do with a lazy mixup of the sound rather than mixup of the meaning? (Not that there’s any excuse for them being in something published.)