The most annoying issue I've encountered are instances where I'm trying to replace text in the middle of a post in order to rephrase a sentence I've already written. I highlight the word and start typing a replacement, but autocorrect clings onto the old word, and when I press space, I end up with both words mashed together instead of just the new word. I have no idea what causes it or even how to replicate it because it isn't consistent, but it baffles me why it occurs.