There's a difference between comments and upvotes. With articles like this (which I really liked), I certainly upvoted it but because it's so technically detailed, I don't have anything useful to add.
Same here. I really enjoyed reading it, but I don't understand a lot of what it is talking about. I also bookmarked it. When the post had 0 comments I was tempted to post something to the effect of what I just said, but I figured it didn't really add any value.