Reading this, and the original thread linked above (which I don't recall seeing previously), prompts me to these observations:
The death of a young man impacts other young men more profoundly because it disrupts their sense of invulnerability. This is a natural "shield" that many young men have, that makes them inordinately brave, or perhaps reckless at times, that doesn't allow them to imagine their own deaths. You see it on US television reality shows, where young guys devise the most crazy & dangerous stunts.
We can read about deaths around the world all day long, but when it's a face we already know then it hits closer to home. And this guy didn't have to be a porn star, it's really irrelevant how he was known to us. He could have been any figure known to the public, even to that smaller segment that watches gay porn.
Another element is the "leading man" factor. TV and films condition us to expect the handsome leading man on the screen to seldom die. That's what supporting actors and extras are for, often chosen to be not quite as handsome as the star. They are expendable, but the star survives right until the closing credits. By that formula Sean should not have died, it broke the rules we've become accustomed to, it startles us.
And it startles and upsets us more if we're close in age to him (22) and find our self-image of invincibility shattered, an unwanted reminder of our frailty & mortality. A phrase you might hear is "Life begins at 40", but it can also end at 22, something we may very much not want to be told about.
And so when it does happen it bothers us, it upsets & touches us, and we're moved to comment online about it. I think it's entirely natural, even if it may not matter much in the cosmic scheme of things. It matters in the things that touch young men when they are 22, and learn that any life they once knew has been snuffed out so early. A chilling thought when you're supposed to be invulnerable.