I took a look at the example articles and I just want to say that for a 13" macbook retina display with default 2x scaling at 1280x800, I found the font size to be a bit too small and thin. I personally liked it a bit more at font-size of 1.2em with a font-weight of 400, but that could use some fine tuning perhaps. I think the main issue is that using pt can be a problem, em/rem would display more consistently across screens.