Very interesting, it would be great to run a diff on the noms from this and wikipedia
Wiki body text is 0.8em in the vector skin, at default zoom I think default is 16px so this becomes 12.8 px in Firefox and 13px in Chromium. Agora input fields are the same size, Agora labels are 11.5 (Firefox), 13px / 12 px (Chromium). This is below the 14px and 16px peaks in the chart in the case study.
Our line height is 150% (1.5em of 12.8 thus 19.2px), which is close to their norm.