But don't wikis commonly have a "Talk" section or similar? The pages that are posted and edited would surely fall under author-generated content.

I believe a lot of the internet has social aspects. Is it possible that the "social" aspects of this media operate on a sliding scale?

I understand the point that literally any website could be thought of as "user generated"... I've personally made quite a few websites. But the level of interaction and the modalities of how I and a lot of folks use things isn't as interactive as, say, twitter.

So, perhaps for some user populations a Wiki is a social experience, especially for the folks who edit them. Though from my perspective, it feels entirely possible to use it without engaging in that social aspect.

I don't feel the same about Hackernews and/or reddit in general.

The social aspects absolutely work on a sliding scale. I completely agree. But I don't think that the amount or variety of social engagement is what really contributes to something being classified as "social media".

Well, how are you defining social media?

I feel like "user generated content conducted between specific users, tied to specific accounts, where users have one-to-one public conversations and those conversations are foregrounded as the site's content" is reasonable.

So, if that's my definition Wikis aren't social media and HN would be.

But I also feel like HN is just a flavor of Reddit, and I feel that most people understand Reddit to be "social media".

I could be worng about those feelings.