The opposite of libertarian is authoritarian, not left. The general trend here seems to be more free speech, less government surveillance, more socialized medicine and Universal Basic Income (and by extension, more taxes). If you had to reduce that to a single label, it would be left-libertarian.
Sure there are _some_ wide-spread beliefs here that happen to align with the left, but I would suggest that HN is far more libertarian than it is left-wing.