Sorry. It must be my browser settings. I tried looking at the CSS used by both this site and Hacker news, and it appears that Hacker News is using points as the default body text size, and the other site is using ems as the default body size. Edit: I'm not enough of a CSS expert to know how these differences work out in actual use.

All I know is, the text I see on Hacker News is smaller than the text shown in your screenshots.