Facts:
SA-MP is already been optimized to reduce lags.
Chat is flooded already with 100players+ and we have now 200 SLOTS
Public chat is for ingame not for outgame, could change though
At all we cannot add it as there are too many factors which would make
it unefficient. They would cause flood and spam that is not needed, also
the moderators ingame would have problems on flame+advertising.

Different it would be if moderators+ commands woul also infect chat user,
but that will mean ban on chat = ban ingame.