Including typo in notes

I've seen many editors notifying typos made by the artist and correcting them in the notes (e.g. post #1646306, post #1656729).
Is this necessary? Shouldn't we just correct them within the translation process silently, and leave the rest of the viewers out of it?

People trying to learn Japanese could conceivably be using translated images here to help them, and uncorrected typos would get in the way of that.

Also otherwise someone might try to correct the sentence without realizing it's a typo. It can happen easier with Japanese since "typo" in this case is almost always another legit word with same pronunciation, suggested by IME instead of correct one; it just makes less or no sense in the context.

Hm, I see the point. Thanks for the explanation.