Ultimately this goes back to lack of a mobile-friendly theme
By default, mobile web browsers lay out a page for a viewport about 980 pixels wide, assuming that designers laid out the pages to look good on a desktop PC with a 1024x768 pixel monitor, a netbook with a 1024x600 pixel monitor, a 1024x768 pixel iPad held horizontally, or a window snapped to half the width of a 1920x1080 pixel monitor. A mobile-friendly site can disable this behavior with the following element:
<meta name="viewport" content="width=device-width">
If a website's viewport is substantially wider than the viewport that a page declares, fonts will be illegibly small. So some web browsers perform "font inflation" to keep text readable without needing to zoom in and scroll horizontally all the time. This involves guessing which elements contain body text and which contain less important navigation and decoration. The description of Homebrew Projects is longer than that of other forums and may be just long enough to trigger inflation.
See also articles about font inflation on dbaron's blog
, jwir3's blog
, and Firefox Support