What problem are you trying to solve? This proposal solves nothing. People could simply register accounts for single use (anon1234, anonABCD...), post in a 'AM locked' thread and never use them again!

With the exception of the point Jim raised regarding which AnonymousMonk am I replying to (being able to differentiate between multiple anonymous posters in the same thread) I have yet to see a valid argument for changing anything.

Update: Edited first paragraph for clarity. Fixed closing bold tag.