TxPun is an idea that started a few years back. From the start, I never liked commenting on sites, I thought it was awkward and very hard to keep track of. When I began to use Pun, I immediately thought that it would be great for comments.
There was this one story I posted that generated 100's of comments, the bandwidth alone to display this page was incredible, not to mention the strain on the server. I was using Nucleus at the time, so we made improvements to the NP_PunBB plugin, which I successfully used on this site. The front end has since changed, moved it to Textpattern and didn't bother bringing over the stories, but the forum still lives on.
Over the years, I've seen this radical approach to discussions used on more sites. Ars Technica comes to mind, if you click Discussion on a story, you are taken to a forum, very PunBB like I might add. More and more sites are using forums to house their discussions, it appears my idea wasn't so far-fetched after all.
The web is evolving, and so is the way we post content and discuss said content. In the beginning blog comments were cool, but things change and we have to learn to adapt along with it.