Transhumanist as in there will always be some guy in every biology/medicine thread to talk about how we will evolve as a species, or claim that immortality is achievable or the likes. This is especially prominent here (and was shocking to me at first), because these opinions are not so common otherwise (in society or online communities). I guess it's just the demographics and personal interests of people here that explain this phenomenon, but I was very surprised.
Can you explain more about this "irresponsible indifferent American fat and sick" thing you've encountered? As an American, I'm curious what has given you that impression specifically on HN.
But PT is not seen as viable, people enjoy living in suburbs and being reliant on private cars for anything, culturally less sensible to ecological matters overall compared to europeans (even though in Europe it scales, and I've felt people enclined to think ecologically most in Switzerland and Germany), mass consumption (people really love Amazon... I mean Europeans do too but Prime is less of a thing here).
Also in healthcare threads (which I browse a lot since that's my original field) I've often seen comments about massive weight loss, illnesses esp diet/digestive or diabetus related (like, in a scale I don't see as much amongst my regional communities). Also how people seem to discover once in a while what a healthy diet is (culturally less prevalent in the US than over here it seems).
This is probably especially shocking to me since I have above average interest in these topics, granted. But I'm still very shocked by the US culture which imo shows and prevails here in subtle things. But every now and then I'm like "ah, true, this is most probably an US user". At least it calms down the lust I could have after working there :)
And I am a european, though I don't see libertarian views beeing the majority at all ... rather the contrary ..