Edellus on 18 December 2017
I think it's an error of the styling of the website, as all elements ultimately follow the website's stylesheet unless it's within an iframe. It's on the website's control how things are displayed.
The font-size is indeed attached to the element, but the line-height that produces this effect is in a class of this website.
In the headers available in rich text reply the issue is still visible, just not as much due to their smaller font-size.
