Is it appropriate to email a professor saying you enjoyed their class, after doing well in it?
As my experience of being a TA for multiple courses with various profs, such personal gestures of appreciation are welcomed by the professors. I have actually heard professors refer to the email as something that "made their day". As long as you don't refer to your grades, I don't see a reason why someone would misjudge your intentions, especially after the course has finished.