We have a Phabricator wiki at Dropbox. Some pages have a style where they alternate headings and subheadings, e.g.
Unfortunately the way this is rendered using the default CSS (as I'm told) uses a gray, light font for the headings, and bold, black text for the subheadings, so that one could easily confuse what is a heading and what is a subheading. (Worse, the headings also have a thin horizontal line below them, making the visual separation of the whole page into blocks even more confusing.)
I was told to file an issue here because we don't want to customize these headers ourselves because that would break the ToC generation.