I don't think it's worth pursuing. People can't do anything with the information, really... unless they're going to take note of every player in their games. Except for in cases when you're the seventh player to join any particular Diplomacy pool, there's no way to control whether a public game of yours will be infested with flakes. And that says nothing about people creating new account names to dodge their old reputations.

It also doesn't easily correct for instances when a player had to go into CD for ALL his games at once, particularly when he was playing many at one time. If a player was in (for instance) twelve games and then suddenly lost the ability to access phpDiplomacy for several days (computer failure, emergency business trip, hospitalization, etc.), then to show up with twelve CDs on a blacklist like this might be very deceptive about the player's normal playing habits.