No really, it is technically infeasible. This problem arises because perlmonks chat is partially the central perlmonks server but also a small flotilla of non-perlmonks servers which do things for their own purposes. grenekatz.org is one such server, desert-island.dynodns.org is another, there's another which I don't know the name to but I suppose I could find out. The list goes on.
Most of the chat clients that work with Perlmonsk (including my stuff) pull up one of the XML tickers on a regular basis. The only way these clients know who said anything is because Perlmonks.org said who said what. Once perlmonks.org has said who said something, the chat client continues to know. The issue of making stuff anonymous after ten posts is actually up the implementors of 95% of not-running-on-perlmonks.org clients to do and this would also require each chat client to somehow determine every chatter's preferences when launched (because a number of them don't have settings that stick around). It also requires a change to the perlmonks server where every user's preference setting for this would be open to the public because every user needs to be able to query every other user's setting to decide whether to forget who said what.