Clinton's concession was not simply damaging because it wasn't hacker news--stories of that nature threaten hacker news as a whole.

(1) A story about Clinton's concession contains no information content. Everyone at all tracking politics knew it was coming, and anyone who cared about when it happened could have predicted the timing reasonably well in advance. Tim Russert dying is a story with no hacker news content, but it is at least some information--I sincerely doubt anyone was predicting Russert's imminent demise.

(2) A story about Clinton conceding is divisive to the community. It brings up a topic of discussion unrelated to the topic that brings this community together, and, given the tendency of some people to downvote in order to indicate disagreement, ultimately increases the homogeneity of the viewpoints expressed here. Most people do not find Russert's death nearly as divisive. Regardless of what you think of the quality of Russert's interviews, historical trends tend to indicate that he will be replaced by someone worse at it.

(3) A story about Clinton's concession reminds everyone of how Reddit came to be what it is. This sort of story is relatively benign in this respect.

(4) The story about Clinton conceding--if it had been popular--brings the baggage of continual political stories in its wake. If every time a major media figure dies there is a single HN story about it, HN is not incredibly damaged by this.