edit: hello downvoters, would you be equally upset that a windows 95 machine would refuse to run office 2000?
The device's web browser should attempt to adapt the page to fit the device rather than the site telling the browser how it should adapt to the size of the screen.
And that's ignoring for the moment the burden of testing a website on all possible devices (which is the way we nowadays go about developing commercial websites, and which is entirely wrong, if a website works on one browser it should work on all, a ship which has long ago sailed but which made good sense at the time and was one of the main reasons the web caught on over all those proprietary and fragmented efforts at information dissemination that preceded it).
Considering that the problem exists in the present and is very real, I'm not sure why not being able to write future-proof CSS is a big issue. How often do commonly-used CSS properties (e.g. font-size) become outdated? When was the last time you had to re-write the stylesheets on one of your websites?
>>And that's ignoring for the moment the burden of testing a website on all possible devices
I think the HN userbase is not only capable but also would be willing to perform this testing. Deploy the website on a separate directory (e.g. news.combinator.com/newdesign/etc.) and direct users who opt into the beta there.
Heck, I bet there's quite a few people here who would love to take it on as a volunteer project.
Case in point: the geocities files that were backed-up and are on display from a variety of sources (including mine, but also the internet archive and archive team) are static, no longer in maintenance. The same goes for all of the internet archive. If you want to see that content at any point in the future you had better hope that the browsers are the ones to adapt to the past because the past is certainly not going to adapt to the browser and as the web ages there will only be more of the past and relatively speaking less of the present.
The web is aging rapidly and the current development of modern browsers on modern devices failing to render sites that are only a few years old properly is a worrisome one.
HN is in fact one of the least affected sites in this respect.
But then iPhone happened.
I honestly don't know, so maybe dang or kogir could clue us in. If a significant number of users are on mobile, and it's reasonable to expect that number to increase for the foreseeable future, then placating mobile users makes sense. I doubt that increasing their SEO is really a priority for the HN staff either way.
Also, two out of the three issues on the google site come down to simple typography and UX. Elements being too close together (links, line-height to add my own personal pet peeve) or too small (font size and the oft-complained about vote arrows) or too poorly contrasted (grey text on a lighter grey background) making things difficult to read and navigate. I don't see anything wrong with improving the readability of a site which is meant to be read... that makes the experience better for everyone.