I have never encountered anyone responding to all other comments but mine.
I would consider it weird. Maybe even rude. But if it bothers you (it would be bother me), stop commenting. If you find the hubs interesting enough and you read them for its value, not for getting attention to yourself, then comments are optional.
My recommendation - always question your motivation first. Why would you continue commenting and expecting feedback if you already see the trend?
I respond to all comments, but sometimes I am harsh, I must admit, when I realize a person did not even read a single line and a comment is "You are great!"
Then I check out hubtivity of the "offender" and he/she left the same comment on 100 other hubs with the frequency one comment per minute - there was no reading!!!
That is rude. To assume I am such a fool. I am, but only to a certain extent.