There were multiple reasons why it was not considered an acceptable option, but one of it had to do with the fact that if we limited comments only to paid subscribers, then what happens when a paid subscriber breaks the rules and gets banned?

Is it an all-time ban? Or just a temporary ban, until their subscription renews? What if they deserve an all-time ban? Will that lead to them cancelling their subscription altogether? I think management was (overly) concerned about tying a person's conduct in the comments to their subscription, for fear of lost revenue.