Who is Constable Moore from The Diamond Age, or, Young Lady's Illustrated Primer and what is their importance?

Constable Moore is the man who guards the gate of the Dovetail enclave. The Constable's real name is Arthur Hornsby Moore; he is a semi-famous and now retired General from the Chinese military. He was scarred by the terrible wars that he was involved in; he shares with Nell a history of difficult experiences, both emotionally and physically.