But if everyone is driving the speed limit no one can pass.

you can exceed the speed limit by a certain amount while passing. at least here.

I'd like to see where that's written into a statute book; doesn't sound correct.

It's in the book you have to study when you get your license here in Texas :) you can exceed the limit by 5mph. Have a nice day!

You too!

The reason that I said I'd like to see where it's written into statute is that I can't think of a reason why it would be legal. It sounds like driver folklore rather than law.

Having a speed limit that can be exceeded simply for overtaking (rather than by emergency services) means the practical speed limit then becomes "the limit + 5" in traffic, which increases the chance for collisions (for no reason I can think of).

I'm of course open to being shown otherwise! I couldn't find anything searching for "Texas passing speed limit" or variations, but my license is European, so I'm not sure where to look.

I specifically said "at least here."