While looking at the edit history of this question, there is a display bug with revision headers. The headers overflow outside the bounds of the revision block.
The bug appears to be caused by a lengthy code-block within the initial revision history. Looking at the page source and CSS, the initial revision is missing a set
width (which is set to
460px in the side-by-side view, thus not causing any overflow)
Collapsing the initial revision history results in the overflowed headers to return to a normal state