Hi @PeakProsperity,
Sorry to jump in on your marketplace topic, but I wanted to give you a heads-up that this may not be the best moment to start working on this.
We’re modernizing Discourse’s JavaScript codebase by replacing the widgets system with Glimmer components.
The post-stream is written using widgets, and we expect to start modernizing/rewriting it in the second semester.
Once that’s done, as the post-stream will be rewritten, any work you put on this now will need to be redone, or at the very least, heavily modified.
Hopefully, I have saved you some money. 
That said, about the project itself, nesting posts properly is a really large project to get done right.
In the frontend, you can get 90% of the job done relatively quickly, but as soon as you start using it, many things break, and the other 10% is really hard.
There is a lot of code in Discourse that expects the post to be displayed/read in a linear order.
There are also server-side implications that would need to be addressed, like how to keep track of unread posts, etc.