This sounds to me like it might be hideously complicated, but putting it in here - e.g. a link to [http://foo.com] gets an external link notification icon on its right on the English Wikipedia, and this should show up as appropriate.
Version: unspecified
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=33084
https://bugzilla.wikimedia.org/show_bug.cgi?id=37901