Obviously, somewhere in the mediawiki software there is a list of
non-whitespace characters which can follow the end of a link and still
be part of it. e.g. "[[fish]]es" links to "[[fish]]" but looks like
"[[fishes]]", which is good because one is the plural form, which
redirects to the singular form anyway.
i don't know when or why the behavior was changed, but I recently
noticed that apostrophes are now being sucked into the link, thus
"[[Arby]]'s" links to "[[Arby]]" but looks like [[Arby's]],
which is
bad because one is a swedish housing project and the other is an
american restaurant chain.
In short, a feature intended for easy plural links now also creates
confusing possessive links. I do hope this is an accidental side
effect which can easily be corrected.
—C.W.