Requiring businesses that provide products or services that we've already decided should be age gated to check ID is not the same as requiring all sites to check ID. Stores that sell porn or drugs or guns in person need to check ID. That hasn't resulted in all stores checking ID, or even stores that sometimes check ID (e.g. grocers selling alcohol) checking it all of the time. They only do for restricted items. No reason web businesses can't do the same.
Sites with user generated content already have to have some level of moderation to remove copyrighted or illegal materials (e.g. child porn). So it's not a big difference to say if you want to have user generated content and not be considered an adult site, you need to take down any submitted adult content (or only allow it in adult verified areas or whatever). If HN doesn't allow people to post their amateur smut stories, it could then be unaffected.
Sites with user generated content already have to have some level of moderation to remove copyrighted or illegal materials (e.g. child porn). So it's not a big difference to say if you want to have user generated content and not be considered an adult site, you need to take down any submitted adult content (or only allow it in adult verified areas or whatever). If HN doesn't allow people to post their amateur smut stories, it could then be unaffected.