I'm gonna be a naysayer: this category is way too mature to compete with a slightly tweaked product.
It's not just Disqus (which is 10 years old now and apparently on 750k sites) but also Intense Debate from Automattic (makers of WordPress) and LiveFyre and muut and Facebook Comments. This is what I found searching for "hosted comments system".
How are you planning to become one of the options there? How are you going to beat accumulated 10 years of SEO of your competitors?
Comments system have powerful network effects. Users would rather use existing Disqus login to comment than signup for another service and website owners take that into account when picking a comment system.
Also, while the desire to not annoy your users (be it site owners or comments) is noble, it's worth pondering why Disqus does the annoying thing they do?
My educated guess is that on average it works for their business and brings more users than not annoying them. What they do might be sleazy but it's probably effective and in business you don't always have option to take the high road.
Notice that the annoyed Disqus users still use Disqus, they didn't bother to switch to muut, LiveFyre etc., which all have free options. Their revealed preference (what they do vs. what they say) suggests that Disqus is pretty sticky for them and they are unlikely to switch because the amount of work would be more than hypothetical benefits.
Even without competition this would be a tough business. People (as opposed to companies) are not that eager to pay even paltry $5/month for completely non-essential service. We might all marvel at the irrationality of not willing to part with equivalent of 2 cups of coffee but that's the reality.
That's why those kinds of businesses pretty much require massive user base using the product for free to get %0.1 to pay to sustain the business. And for $5/month you get the worst kind of customers (cheap and entitled).
This is not a good kind of business for bootstrapped/solo/indie person if only because at some point you'll spend all your time dealing with operational issues of launching more servers, debugging issues and trying to provide support when things inevitably go wrong for the (mostly free) users.
Disqus is massive today, they seem like a stable company employing tens of people but it took them $10 million in funding to get there and they don't have a amazing business (or they would IPO by now).
Generalizing a better solo business is one where you can charge $20+ so that you can become sustainable with much smaller customer base and therefore you can attack an underserved niche, rather that competing with companies that already have hundreds of thousands of users and massive SEO advantage.