"Plane change maneuvers are expensive" is the one I remember off the top of my head, but I do distinctly recall another line elsewhere in the book. Sorry I can't be more specific.

Plane change maneuvers _are_ expensive; reusing that sentence can't possibly detract from a book.

Rephrasing such a sentence undoubtedly requires far less energy than the delta v necessary to accomplish the actual maneuver.

Coming up with different phrasings of the exact same concept per book is potentially more expensive in terms of suspension of disbelief.

"Why is she taking a whole paragraph to say, 'Plane change maneuvers are expensive'?"

Why bother? It's not like Stephenson invented that sentence. It's a fact, stated in the simplest possible way. If you google that literal sentence, you'll find quite a few uses unrelated to his books.

Want to take a swing at that yourself? I did do some google searches for the phrase in question, and other people have used it online (though I admit all the citations I found in my cursory search date to after Anathem, though that is no guarantee that they are aping it.)

No comment on re-use or what-not, but:

https://www.google.no/search?q=Plane+change+maneuvers+are+ex...

I noticed a lot of parallels between Snow Crash and Anathem. Both had dialogues meant to educate the reader, and there is a little overlap in the concepts explored in both books.