I created these patches somewhere around Gaim 2.0, and they still work as of Pidgin 2.4.1.
I can sort of understand why the Pidgin developers decided that colors, italics, etc. should persist from message to message: It means there doesn't need to be a separate UI for configuring the defaults. But I'd much prefer that there be a "use this as default formatting" button for the people who want it and that the formatting reset to that default every time a message is sent. This patch doesn't bother with the button (though "Reset formatting" is now available in Pidgin itself), but it does automatically reset your formatting each time you send a message.
CTRL+L clears a conversation history from the window. I never want this, but I occasionally press it when I mistakenly believe that Firefox has focus.