The discussion you are thinking about is neither dead nor flagged. Overly active discussions get downranked automatically:
„Other factors affecting rank include user flags, anti-abuse software, software which demotes overheated discussions, account or site weighting, and moderator action.“, see https://news.ycombinator.com/newsfaq.html
It's not perfect, but it really does often correctly identify flamewars. If you feel a post has incorrectly triggered the flamewar detector, email mods at hn@ycombinator.com.
As I write, this thread doesn't trigger the criteria.
„Other factors affecting rank include user flags, anti-abuse software, software which demotes overheated discussions, account or site weighting, and moderator action.“, see https://news.ycombinator.com/newsfaq.html