Here's our approach to writing complex, branching, and meaningful conversations in our indie adventure game Postmortem: one must die,
which has been often complimented for it's intricate dialogue:

... an example of how to write nuanced characters with a reach into complex late-game branching narratives ... which happens little elsewhere in videogameland.
- Cara Ellison, PCgamer.com

... video games can function as a medium for important messages and Postmortem is a prime example of that.
- Cassandra Khaw, USGamer.Net

It took many attempts to figure out a good way so sharing the lessons. We broke the process into following steps:

• The Editor – setting yourself up right
• General Concept
• Distill and Make game-ready
• Conversation Outline
• Narrative Beats and Branching Filler
• Non-essential side branches
• Test, Refine, Repeat

READ full article HERE!
(note: I wasn't sure if this should go here or in Writing but figured since it covers design aspects of characters and convos as well it would be more useful here. Feel free to move mods )

Thanks for sharing, all I know is that branching can massively increase complexity, I have attempted a game story with 2 way branches at each zone/level, and this quickly became difficult to manage, so I changed my story and basically inserted the other level paths into one storyline. I never actually made the game. I think with good tools branching in text is more possible (and less likely to cause problems).

Wow! This is really cool stuff, thanks for sharing!