ונוהגין להפטיר בחתונה שוש אשיש.
The Rama above (from OC 428) says that in his area the custom was to read a special haftora if a groom was present in the synagogue.
Has anyone seen this minhag or know why it seems to have largely died out?
Wikipedia claims (with no source given) that
This is a revised edition of something I myself added to that article in 2004. While I didn't cite any source (and, still, there's no citation for that claim in the Wikipedia article), I do remembering having researched the issue, and I feel confident that my self of several years ago would not have added that information without its being IMO reliable; alas, I no longer remember what the source was.
Edit: Note, though, that Shaare Efrayim 9:26 says that "some places" do read this haftara but that "we" do not.