Let's take the first case. https://codepen.io/webcompat/pen/NWOOzyp?editors=1100 :link applies the background-color and not ::link But if we go to https://codepen.io/nhoizey/pen/gOBBeEz This :link is not applied. Funnily enough if I do ::link instead, then the background-color is applied. That might be related to parsing rules.
<rdar://problem/109508572>