In darkness our eyes can easily detect a 1W LED from kilometers away.
But can they distinguish a specific 300 mW LED in a stadium with tens of thousands of other LEDs next to it?
If it were a different color, yes. If each of them were a different color, your eye would still be able to, as long as you had enough focus. So the analogy holds pretty well.
My understanding is that healthy human eyes are able to detect individual photons.
No. Amateur radio operators have done it, and it’s not difficult to imagine how one would.
Indeed, nothing is difficult to imagine how to do if the method is common knowledge.