Not to detract from the good overall point, but isn't the math here a bit wonky? In the first example, he shows 160k insertions and 130k deletions and claims that therefore he wrote 160k + 130k = 290k lines of prose. That's... wrong? He wrote 160k lines of prose. If you want to express it as a sum, it's 160k (total inserts) = 30k (current size) + 130k (total deletions.)