All thanks to a quirky bit of software produced to alleviate the pain of a tiny subset of a very small audience.
One more little contribution to the useful PhpCss selector parser by Thomas Weinert. In this case, the regular expressions were greedily including combinators in pseudo-class literals, instead of seeing the end of the token.
Before: it saw
a:hover>span and errored, saying “there is no such pseudo-class as
After: it sees
a:hover>span and putters along happily with element
:hover, child combinator
>, and element