What's uncomfortable about browsing with a full-size window? I usually find it slightly more painful not to have the browser maximized.
HN specifically, if I have serious reading to do in the comment section, I might narrow my browser down to 600px for even better readibility.
There were a few years that I configured my work machine to have dual monitors in portrait mode. That helped my feeling of constriction, while giving shorter lines of text. As a bonus, it matched pretty closely to the 1280 width (at 1200 pixels), and often allowed more of the text to be shown at once.