[Analemma_]

HN upvotes jokes all the time. As for porn, it would be removed by the moderators the first few times, but if a majority the community decided it really wanted it, it would eventually push back on the moderators and the moderation standards would change (well, or YC would just shut it down). At that point it would be up to you whether you wanted to keep coming here, but at the end of the day there's no real way for a vote-based system to perpetually override what the community wants. In practice it works because we're mostly interested in the same things and mostly agree on what isn't appropriate, but you do get edge cases like this.