I can't really disagree with him though, Reddit really is a Digg clone minus the UI.
The reason they're so different is that they have different origins. Digg started as Slashdot with voting instead of editors, and reddit started as Del.icio.us with voting instead of saving.
Digg still orders comments chronologically and that sucks. I'd equate this with google not paying attention to ordering of results! Creating a threaded comment system without the ordering is so mind numbingly easy and digg decided to take the easy path without paying attention to the details that count.
I was tempted to post this where the creators of digg can see it, but I don't really want them to realize their error:)