I disagree. Line to line is not the overlap with earning, it has to be on the same line. (the n and a below it are not a valid example)
As far as going back and inserting letters, of course that is possible.
Do you have a clean example of typed kerning?
Don't you see that in both cases in my little example, that where an 'a' follows a 't' that it is closer to the 't' than would be expected? Kerning is nothing more than determining the position of a letter based upon the letter it follows. That's what seems to be happening here, but I assure it is not.
ML/NJ