Notices for redundant operations

I found a few notices and warnings that inform you that the command you
are executing has no effect because the object is already in the state you
want it. I think these are useless, and there is also some inconsistency.
Does someone want to defend keeping them?

=> alter table test set without oids;
NOTICE: table "test" is already WITHOUT OIDS

=> alter table test cluster on test_ix;
NOTICE: table "test" is already being clustered on index "test_ix"

=> alter domain foo set not null;
NOTICE: "foo" is already set to NOT NULL
[no such notice for altering a column, btw.]

=> listen foo;
WARNING: already listening on "foo"

=> alter group test add user peter;
WARNING: user "peter" is already in group "test"
[The SQL analogue with roles does not call for a completion condition in
this case.]

--
Peter Eisentraut peter_e(at)gmx(dot)net