When you quote something, the software just pastes text into an appropriately formatted box. It doesn't read the original post beyond that. This is likely done to help archive the content of a post at the time it was responded to; that is, before any edits to said post. (Don't look at us. We didn't write the software.)
In my decade or so of experience here, changing quoted text has pretty much never been an issue. If someone was ever so petty as to blatantly misrepresent someone in that way, they would be asking for a swift end to their participation here, to which we would gladly oblige.