if it were flagged, it would show as [flagged][dead]. Looking at the submission history for the domain, they've all been [dead] for years, so clearly the domain is banned.
No idea, certainly the HN spam filter isn't perfect. You can mail the mods and ask about/ask for it to be unbanned, in my experience they appreciate people reporting false positives to them.
https://news.ycombinator.com/item?id=32994573 pointing to:
https://www.volcanodiscovery.com/earthquakes/quake-info/7054...