If anything it's the reverse I'd think. Just look at books without a Happily Ever After and how that's looked down on, and why its a requirement for Romance publishers.
Yeah. Though the third party users are probably are the heaviest users so probably have an outsized impact on the content of various subreddits. So no, I don't think the lack of 3rd party clients and those users will kill Reddit, anymore than its killed twitter or Tumblr shennanigans has killed tumblr. That said I did just join today, and I do actually wonder given the death of 3rd party clients and the IPO when reddit will try to squash NSFW subreddits and posts. Thats the kind of thing I'd expect as they IPO and chase advertisers.
Us Aussies sneak into the top 5, yay.
As for the age thing, I'll just say I have posted to usenet :)