password in pg_shadow

Is all in next example good? See:

abil=> CREATE USER myname WITH PASSWORD BuBuBuBu;
CREATE USER ^^^^^^^^^^

abil=> select * from pg_shadow;
usename |usesysid|usecreatedb|usetrace|usesuper|usecatupd|passwd |valuntil
myname | 5808|f |f |f |f |bubububu |
^^^^^^^^
(4 rows)

Why is in pg_shadow.passwd low case only?

Zakkr