I usually, but not always, try to give a little hint in the 'thank you' message for the karma as a subtle reminder as to what post the karma and thank you, and the karma message, are referring to.
Sometimes I'm halfway through typing the karma message and hit some odd key sequence and accidentally send some incomprehensible message.
It would be nice though, if karma was set up like the private messaging system, where you could switch between incoming and outgoing with a reference to the actual post in outgoing karma and the karma message you sent. Something do dream about, like a firmware update for my PRS-700 that will allow dictionary look-up and scribble notes.
WDE.