One of the most mindblowing things is when I hear about someone playing one of my games, because it so rarely gets back to me. Darkest Hour has over 7k downloads, so i figure at least a few people must have played it
Something I found that really helps writers especially is to tell them you read their work. There is a friend of mine who thought their work went completely unread for ages, they had no idea, I would read every update of theirs no matter how small.
I told them their work was important to me.