I will be using the diff construct from now on, it’s helpful.
I don’t see Discourse implementing that other suggestion from the Gist, the more I think of this, the more I believe it would fit perfectly inside the syntax highlighter, not outside.
Basically, as years go by it makes sense to add some features to syntax highlighters, and the basic job of showing code in an easy to read way extends naturally to show also some of the code’s dynamics.
What changed, where, by whom; what am I pointing at; which helpful comment explains the relation of the code to the place where it is being posted, etc.
Thanks to everybody for their participation in this discussion.