Nothing strictly happens for not explaining an edit. Generally it’s not against the rules or anything.
Usually it’s good practice to note an edit if it affects the context of people that already replied to you. Like if someone points out a factual error and I fix it, I leave the original text crossed out so the other person doesn’t get a barrage of people telling them they read my comment wrong.
On the other hand, if I just happen just notice a spelling error or whatever and fix it, I won’t note the edit. Additionally, edits in the first minute won’t actually mark comment as edited, specifically because it’s usually tiny things like that.
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