Here's an important tip for SCP topics. Ignore anything Bryan See says, he doesn't know what he is talking about.
Yes, there is a mostly dummied out "feature" that creates an exclusion zone around an object named "planet", but that's as far as that thing ever went.
The mission space limitations, unlike what Bryan said, don't have anything to do with the renderer; the bigger issue is that we are unable to guarantee that physics still work that far out.
Plus, given the speeds FSO is built around, you'll never want to have a mission that would use that much space anyway.