GMail is really so cool. I think rather than just relying on quotation marks (> and such), it strips them and then diffs the message to its predecessors to find common chunks. I saw that in action when I sent an updated patch to a mailing list. In both versions, there were no quotation marks, but the second message, viewed in GMail, showed just what had changed versus the first message, the rest being hidden behind "--Show quoted text--" markers.
Literate testing, JCite, Java, Excel for Java, Mercurial, and whatever else seems to long for a tweet.