How would you modify Reddit’s UI to rapidly visualize long, branching reply chains?

I'd like to build a website that is kind of like Reddit but the purpose is to have people collaboratively tell stories by chaining their responses to each other. so person 1 writes a sentence, person 2 responds with a sentence, person 3 responds with another sentence, etc. all the way out to 100+ submissions.

Further, if people don't like one of the sentences in the flow, they can add ANOTHER sentence parallel to it instead (but branching off the same previous sentence).

So as you can see it's basically a long branching tree of sentences.

How would you visualize this? In the Reddit interface, that would become unwieldy because the horizontal real estate it would take is just too wide, it would be impossible to see smoothly on one page.