I'm in my early 30s and I usually use "!" to convey genuineness. For example "That was so helpful! Thank you!" or "It was great to see you! Thanks for dropping by while you were in town!"
>"It was great to see you! Thanks for dropping by while you were in town!"
They didn't already know you enjoyed seeing them? Saying things like that after the fact instead of to the person's face as you said goodbye is more "old person behavior". You sound like a Facebook user.
