Yes, and it has replaced what Disqus was in at least a site already.
With it, anyone can use Discourse, and even at our free plan, to host a comment system for their site, and keep full control of the data, appearance, extensibility, etc.
That is the exact use case we had in mind when creating it!
You actually hit the nail on the head here, I do recommend going to a recent blog post in our blog, like Discourse is Not Going Closed Source and checking it live now.
Does this create a new topic if non existed … so if we have a post or page and we enable comments do we have to manually set up the forum post before hand or will it create on first use?