If an email that wasn't part of the public debate was altered, who cares? The simple fact is that, of all the emails that were covered by the media, the Clinton campaign was unable to point to a single one and say it was altered.
It looks like a very large number of the emails from podesta's inbox weren't signed. I have seen no evidence that all or even most of the emails that were part of the public discourse were actually signed.
Notice I never said all or even most of the emails were altered.
That some of them may have been subtly altered was one point of my argument.