Note to self: pseudo elements, line-height, rem and IE

It seems there is a bug in IE9-11 which causes line-height to collapse in psuedo-elements when the line height is set in rems.

The bug was reported by Matt Stow over a year ago in relation to IE10 but nothing seems to have been done to rectify the issue.

The best workaround is to set the line height in an equivalent px value instead.