Yeah, I feel you. You feel like a klutz when it happens, and it's compounded when longer comments that you put effort into fall prey to this. A little something that I learnt from Reddit is to tack on a new paragraph headed by "EDIT:" making a note of corrections made or adding more text, followed by "EDIT 2:", "EDIT 3:", and so on, if necessary. It's a good-faith gesture from your end, and it eases the shame a bit.