I almost asked this question myself. When I first started writing for hubpages I accepted every comment eagerly and never considered denying any of them.
Now that I have been writing for a year, I receive at least 1-5 comments daily. Many of the comments I receive relate to requests for an interpretation of a dream. Sometimes the dream is relevant to the hub, sometimes it is not. Sometimes I am unable to understand the comment due to grammatical and spelling errors. If the comment was written by a fellow hubber, I can contact them but most of these comments I have received are from anonymous commenters. I have not denied them but have not approved them either because I am not sure how to reply and their comments request feedback from me.
I haven't made a decision yet about which comments to deny but I certainly have received many comments that are requests I do not understand or know what to do with.
This question was helpful since I could understand what others had to say. I agree with the others- if a comment was profane, violated hubpages rules, or was inappropriate for minors reading my hubs I would deny it. Luckily, I have not received any such comments.
I definitely see both sides. On one hand, approving all comments and supporting our readers should be our goal.. On the other hand, some comments could be confusing or unrelated which could affect other readers who read the hub. I