J'ai relu votre question initiale et j'ai trouvé la solution suivante :
SELECT *
FROM users
WHERE id IN
(SELECT id
FROM users t4
INNER JOIN
(SELECT soundex(fname) AS snd,
COUNT(*) AS cnt
FROM users AS t5
GROUP BY snd
HAVING cnt > 1
)
AS t6
ON soundex(t4.fname)=snd
)
AND id NOT IN
(SELECT MIN(t2.id) AS wanted
FROM users t2
INNER JOIN
(SELECT soundex(fname) AS snd,
COUNT(*) AS cnt
FROM users AS t1
GROUP BY snd
HAVING cnt > 1
)
AS t3
ON soundex(t2.fname)=snd
GROUP BY snd
);
C'est un peu trop compliqué, mais cela fonctionne et fournit exactement ce que vous avez demandé :)