Sure, and equally obviously there are a lot of users below the median/mean. Millions of them, in fact. Some are below the poverty line.
HN is more varied than you're assuming. That is actually the leading problem facing the community. People develop a distorted image of what the HN community is, and then when they encounter posts that contradict their image, they resort to antagonistic explanations that are harmful.
The actual dynamic is this: many people here have wildly different backgrounds, and therefore strongly different views, than your own (I don't mean you personally, but all of us)—views which they come by as honestly as the rest of us come by ours. Yes there are bad actors, but users grossly overestimate the significance of that. We're far too quick to consign each other to the bad actor bucket, because we underestimate the variety and size of the genuine differences between us.
I'm not saying that it's exclusively people below the median/mean, I'm saying that due to the content the site focuses on the board is going to skew towards the more wealthy in whatever market they live in. Obviously I don't have the demographic data to back this up, but it's just the reality of the situation. Inside the US, this board's users are going to be wealthier than the average US population. I suspect that would hold true for any group you look at, whether its a global perspective (probably even more skewed if you look at the global average wealth). Beyond that, you need an internet connection at all to come here, so right there you're going to be skewing wealthier than you would if you picked an "average".
I'm not consigning anyone to the "bad actor" bucket, but when we talk about filter bubbles we should at least be honest about the composition of groups and what traits they might have. There's no reason to think that the average HN user is representative of the average individual given the content.
Beyond that, due to the upvote system, the majority is amplified, so even if there are millions in poverty on this site, their views are going to be pushed lower than the tens of millions not in poverty. This is a bigger problem than HN obviously, but it does nobody any good to deny it's existence. The same could be applied to any minority group, whether its gender, sexuality, or race for that matter. This is a consequence of the system and you see the same thing on various subreddits (the fact that they split things into smaller boards mean there are communities where the site minority might be able to actually have a larger voice than the majority)
I don't disagree with that. It's just that it still leaves many people, hundreds of thousands if not millions, who fall outside the description you're making, and thousands of them post comments here. There's simply a lot more variance in the community than it feels like there is. That mistake has a dramatic effect on discussion.
Edit: I was replying to the first version of your comment. I do disagree with the part you added later about upvotes. I think it is overinterpretation of the sort that feels-like-it-must-be-true, or feels-like-it's-probably-true. If there's one thing I've learned from moderating HN it's that those perceptions are extremely in the eye of the beholder and need to be bracketed if one wants to assess anything objectively.
p.s. Just to avoid misunderstanding, your account is still banned because you've continued to break HN's rules since we originally banned you. I restored your comments in this thread in order to reply to them. Users can also do that by vouching for good posts which shouldn't be [dead] (this is described at https://news.ycombinator.com/newsfaq.html#cvouch).
> a lot of the American userbase on HN are not "well off"
Oh come on, get serious. This is a board focused on Tech, an industry where our the median/mean is well above almost any other field in the US.