Comment 3 for bug 315399

I run into it regularly with HTML. Imagine that x is "<th>" and y is "</th>". Working with HTML seems to trigger this and similar-thought-not-necessarily-related things like bug 278346.

In the time that lead to me filing this, <th> was actually about 60 characters of stuff, so it took a long time reading char by char and then manually checking whitespace to convince myself that I HADN'T changed that line.