I liked Cove Comments enough to buy a year’s licence.
My trial of Cove Comments expired, and I am happy enough with the service to buy a year's subscription. It's easy to use, integrates with my site's membership features, allowing any member of the site to comment on a post. Short of writing a comment plugin myself, which I can't be stuffed, it looks like the best commenting system for Ghost by a long shot. Yes, I'm not thrilled about adopting yet another subscription, but I'll give it a year and if I really like it (and my members actually use it), I'll look at buying a lifetime licence.