I brought this up earlier; he issue is due to the “system font stack” approach used for the monospaced font, which results in a font that, depending on the platform, OS version, browser and user fonts installed, may or may not match the size of the PEP prose content. Using a standard web font (e.g. Incosolata) would resolve this, as it has a consistent size on every platform, but others favored the “system font stack” approach for other reasons, and thus far the discussion has not reached a resolution: