I just retried viewing this page after rebooting into Windows and it looks completely different. The text is a lot smaller than on Linux. So Windows handles HiDPI a lot differently, it seems. But my own website looks exactly the same on Linux and Windows. I'm using a "reset.css" --- maybe that's what's at play here.
In any case, our impressions being different only prove my point about standardized styling of webpages.
In any case, our impressions being different only prove my point about standardized styling of webpages.