I don't make comments for the sake of making comments. If I think I have something to add to "the discussion" I'll add it. If I really find something especially good about the Hub I'll comment.
I always vote up (although rarely I may forget), whether or not I comment. I often also click on the "interesting", "funny", etc. buttons as well as voting up. The main idea with commenting is generally supposed to be to comment when there's something meaningful we can add.
A lot of people don't like this kind of thing at the bottom of their Hubs:
"thank you for writing this Hub"
"thank you - and you're welcome"
........(that kind of thing). It adds nothing to the Hub, really. A lot of the comments people think up for the sake of making comments are obviously just longer versions of what's above.