> If you're instead changing your argument to say that it's impossible to do _well_ What? I didn't change my argument, that's what I said in the original comme

> If you're instead changing your argument to say that it's impossible to do _well_ What? I didn't change my argument, that's what I said in the original comment you replied to. All of your examples are things that _don't_ happen while you're typing. If you want to dispute my statement that all formatting should happen on blur, fine; you can expand that to include any time the user isn't typing. The issue is when you format the text while the user is actively trying to enter it, you'll mess up the cursor position and easily get into a situation where you can't add or remove a character for some reason because the formatting considers whatever you're trying to type invalid. And you'll also notice that I explicitly said in my original comment that you can't get it right _all_ of the time, and those times when you do get it wrong prevent the user from completing their task because of a superfluous feature. This is terrible UX and once this happens to a user they will never trust your software again.