How hard is it to type .com? And why should the YC admins be encouraged to create a 'news' subdomain just to work around your laziness?
Also, I don't know about the flexibility of news.yc's custom Arc webserver. I suppose it might be much more work than adding a new VHOST conf file.
Technically speaking ycombinator is a subdomain of com and news is a subdomain of ycombinator.com and so on.
www.news is not a valid subdomain name afaik, because it incorporates the separator in to the domain name.
So to make things work like you suggest a subdomain of news.ycombinator.com would have to be created.