One of the joys I had when teaching was a student acknowledging the course was useful.

  The level above was a course "interesting", "great", etc.

I remember two specific cases:

• one student coming personally to thank for the course. It was the last of their years, and after marking, so the "thank you " was genuine. It was not even a great student (he got something like 14/20 which is a so-so mark)
• one other student coming to say the the course was interesting, that she learned a lot and that if she was to ask one thing for the future students, it would be for me to speak slower (the course was in English in France). That was a fantastic feedback: a nice one and constructive on top.

So definitely yes - tell him/her you enjoyed the course without overthinking.

One of the joys I had when teaching was a student acknowledging the course was "useful". The level above was a course described as "interesting", "great", etc.

I remember two specific cases:

• one student coming personally to thank for the course. It was the last of their years, and after marking, so the "thank you " was genuine. It was not even a great student (he got something like 14/20 which is a so-so mark)
• one other student coming to say the the course was interesting, that she learned a lot and that if she was to ask one thing for the future students, it would be for me to speak slower (the course was in English in France). That was a fantastic feedback: a nice one and constructive on top.

So definitely yes - tell him/her you enjoyed the course without overthinking.