I would use "tells" because it's a good use of the simple present - a habitual action or general truth.
Originally Posted by Will17
I'll say "Thank you. That was so nice to hear!"
I'll say "Thank you. That makes me feel better" would apply if there was a problem and they told you that it wasn't your fault or that they had made the same mistake in the past.
Barb, you have such a great smile. You light up a room when you laugh.
Oh, thank you! That's so nice to hear!
Oh, Barb, don't let this bother you so much. I assure you, I had the same thing happen to me, and it worked out okay.
Oh thank you. Knowing that you made the same mistake makes me feel better.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.