Obtener una media de más de 10 méritos por día es casi imposible, aunque algunos lo consiguen en ciertas rachas (ver
).
En lo relativo a la Actividad, supongo que sabes que los 775 es el umbral inferior de una ventana que va desde los 775 hasta los 1030, en la cual uno puede rankear como Legendario. El valor concreto que le corresponde a cada persona es desconocido, y se obtiene a partir de aplicar un SHA sobre el IdUsuario + una constante secreta que sólo conoce @theymos:
Can you make getting legendary provability fair? So we know if you don't like us that we get it anyway

Nah, that'd significantly complicate things. Currently this randomness is done with a single SQL query, which is very convenient.
update smf_members set ID_POST_GROUP=21 where ID_POST_GROUP=8 and
activity>=775 and activity>=775+conv(substr(sha1(concatenar(ID_MEMBER,
secretSeed)), 1, 2), 16, 10);
The required activity level per user is suitably random for betting, but anyone who can read my code (there are a few such people) will be able to exactly predict when someone will become Legendary, so I don't really recommend it.