ValveSoftware
Story dialogue skipped via alt route in sp_a3_portal_intro
Using an alternative route in the specified map causes important dialogue to be missed. Specifically it's when Cave turns against the "make lemonade" idea and discusses putting Caroline in a computer. Screenshot of route:
http://imgur.com/9zqnG8E
This is instead of the expected route, putting white paint on a sloped surface and propelling yourself onto a platform to the left of the area in the screenshot. Heading to this area after doing the alternative route still triggers the dialogue, but is not necessary to continue and thus allows easy bypassing of important story details.
System info:
https://gist.github.com/GlacialTurtle/4de36032216a74da3d06
Do you find a route on Linux which is different to what is available on other versions of the game?
Not as far as I know. This area in particular very deliberately allows you to place white paint almost everywhere, including the place in the screenshot. I may have portal 2 in windows still installed, so may retry there and see if the same thing happens or if it allows me to reach the platform. Note the only significant route difference is where you place the exit portal, so long as you gain enough momentum falling through to get high enough to reach.
Just tried it in Windows - same thing happens and dialogue is simply not played. Not Linux specific then.