If it was a private thing I would be totally with you, but the black bar's entire purpose is to send a public message to the community. It seems natural for the public reading the message to wonder why it was sent (or omitted) on a given occasion. It's not "why aren't you grieving?" but rather "what message are you trying to send us through displaying or omitting it?"
The public message is that "someone who has had a profound impact on YC, or HN and its members has passed away". That impact is up to the operators to decide.
Much the same way a family remembers their loved ones, but doesn't grieve every important person who has passed away irrespective of their stature. Like parent was saying, it's a little discomfiting to see this discussed on threads.
