I do. I'll compliment the model or give it a thumbs-up emoji. If you watch a model's thinking stream you can see that the model is always attempting to assess the user's intent, including emotionality.. '...the user is expressing uncertainty about.. ' or '..the user is expressing appreciation for..' etc. and this influences the overall response and sometimes even their decisions. It's a language model, so why not use language to convey info about what you're feeling to the model, it understands that language too.
I have this superstition that if I praise correct outputs, the model may use this information that previous output was correct to produce better answers in future turns
But this only makes sense in the context of a new ask, and not as a standalone message