I say leave a comment. I think all, or at least most, writers appreciate comments generally. Kind of like a face to face conversation: Sometimes you have a lot to say, sometimes you don't have much to say. You know, like when you are talking to someone and what they've said is rather complete, you might just say, "Exactly" or "I like that, you nailed it", you know, something along those lines. As far as a Hub goes, something basic might do like, "Very enjoyable read" or "You really nailed it" or "Great piece, enjoyed it very much". Just throwing those out there, it's up to the commenter how to put it. Mainly, I think it's a good thing to comment; it shows the writer that people are showing interest in their work. I've read on here it might have an influence on traffic, but I don't think that's been confirmed; but a comment is kind of like new content, so it follows it might influence traffic. Here's something I'm pretty sure happens if I remember correctly: When a comment is made, the commenter's followers get the Hub in their feed.