Wrong wrong wrong wrong wrong interpretation.
From the same chapter:
“Canceling guilt” and “doing away with punishment” are not part of the language of penal substitution, and I am wondering if you left out the last part on purpose, since its right after where you cut off the paragraph. By canceling guilt Christ removes guilt from us, and by doing away with our punishment Christ removes the need for it. Thus, He took our punishment in that He took it away, or “did away with our punishment” as stated by Augustine himself. Either you were dishonest in deciding the cut off point for your quote or you are only seeing what you want to see from Augustine.
Yes, Christ took on our nature and therefore suffered death for us, in order to repay our debt. Though He himself was blameless, He died because the wages of sin is death. So, because of our sins He suffered death. Hence Augustine says “Confess that He died, and you may also confess that He, without taking our sin, took its punishment.” What Augustine believed was called substitutionary atonement, and is very different from penal substitution. In penal substitution God has to punish someone in order be able to forgive man, so He punishes Christ. In substitutionary atonement the debt of sin must be repaid, and only He can do it, so He sends the God-man. Read about it before making leaps that you should not.