I'd say that for a hub to be interesting to me it would have to strike a chord of either harmony or dissonance. If it's harmony that I feel in it, then great, I'll be more likely to 'follow' the author. If it's dissonance, then I'd be more likely to comment and mention what I feel is a flaw and why.
There are things also that I may have a random curiosity about that may draw me in as well. if it's well written I may comment as well. I wish there was a way to set book marks within hubpages so one could get back to them as a reference in the future.