Why?
Seriously, it seems like a genuinely nice note. No harm was done and everything that was said was validating and positive. It didn't need to be said, but that just makes it all the more special. That guy going out of his way to give that validation when it obviously wasn't necessary just shows that he isn't just being a good dad. His parenting is at a quality at that at least one other dad admires. He doesn't need to be told that, but I'm glad he was.

I suppose I don't understand your perspective. If you know you're a good dad then getting validation on top of that is just good, right? If it's obvious you don't need it and someone else is still compelled to tell you then you must be doing an even better job than you thought!

It's good you don't need validation. In fact it's a great level of confidence in your ability. So if someone validates that confidence. That's good? It's not needed, but it's still good.

Or at least that was my takeaway, I was curious about yours.

ETA: I had a thought... What would your opinion be if the feedback was negative? What if he was aggressive and mean? Not loud, or drawing attention, just a dickhead to his kids and family.
I'm not looking for any particular answer here, I'm just curious if your opinion would change at all.