A version of that was attempted on Fluther once upon a time. During the trial, if the querent awarded a quip with a GA, then the “Great Answer” link was colored red for all to see.
I personally felt like it put undue pressure on the querent to award GAs just to be seen as “fair”. Or perhaps if people realized that certain querents were stingy with GA lurve, then perhaps they wouldn’t answer his questions any more.
It was disabled after only a week or so.
—
On occasion, I will simply state that I’ve given a GA/GQ in a quip if I want to draw attention to it. I think that’s sufficient.