I get it as a cultural thing, but it makes no sense epistemologically.

An unethical person would not state they changed their comment, and a malicious person would state their edit was mundane. Those two factors alone render the practice of proving your innocence in advance moot.

I think it's sad that people reflexively assume the worst. I used to engage in some heated debates on Reddit, but I was never accused of, or assumed the other person edited their posts to make me look bad. It seems like paranoid behaviour to me.

Strangely enough, if it became the norm to correct typos without stating it, the default assumption would be that the edit was a typo correction.