[[André]]a works, [[André]]é does not, [[André]]tá works until the accented character, where "works" means that the whole tail is linked (blue).
It's the same with many accented characters (öâñçś...), but then čćđšž seem to work in wikilink tails.
This probably isn't that new, but is more visible with the new, lighter link colors.
PS
What about [[Batman]]'s and [[a]]''b''?
According to en:Help:Link, they once worked.
The "link trail" varies by language. Which project/language are you referring to?
For example, in English it is
$linkTrail = '/^([a-z]+)(.*)$/sD';
This hasn't changed in 16 years, since rMW5b97a5bbf24f: (Bug 15035) Revert linkTrail to /^([a-z]+)(.*)$/sD, as it was before r36253..
It also varies for many other languages, for example, in French it is
$linkTrail = '/^([a-zàâçéèêîôûäëïöüùÇÉÂÊÎÔÛÄËÏÖÜÀÈÙ]+)(.*)$/sDu';
In German, it is
$linkTrail = '/^([äöüßa-z]+)(.*)$/sDu';
@Reedy, primarily Croatian (hrwiki) because a user complained to me that [[mišić]]ā isn't working (though [[mišić]]a is), but also English, as I mentioned above, because the two examples on the Help page do not look like they should (according to the descriptions there).
I see no reason why [[xxxx]]yyy shouldn't work for all European languages, where y is any (Latin, Cyrillic) letter - accented or not. Would \p{L} work now or is that still broken?
Where can this regex be set? The note on top of MessagesEn.php says "... You can make your customizations on the wiki. While logged in as a sysop user, go to Special:Allmessages ...", but I don't see any message of this kind there.