I'm on HN for one reason: insightful news and commentary that can directly help my startup.

The minute that HN loses its insightful nature or somehow gets its value diluted will be the time I look for something else.

When you say "another demographic" what do you mean? Age? Language? Geographic location? or outside of the tech community? Since the community and content matters, changing the demographics might impact significantly whether something HN-like would succeed.