"text to text" operator redefinition ignored

PG 9.2.2, Windows, empty database

just curious, redefinition of various operators seems to work nicely but
"text to text" operator redefinition (last block down here) seems
completely ignored:

set search_path to public;

select 'aa'::varchar = 'aa '::varchar; -- returns false
create or replace function public.opr_vceqvc(varchar, varchar)
returns boolean as
$$
select rtrim($1)=rtrim($2)
$$
language sql immutable;
create operator public.= (leftarg = varchar, rightarg = varchar, procedure
= public.opr_vceqvc, commutator = =, negator = <>, restrict = eqsel, join
= eqjoinsel, hashes, merges);
select 'aa'::varchar = 'aa '::varchar; -- returns true
drop operator if exists public.= (varchar, varchar);

select 'aa'::text = 'aa '::varchar; -- returns false
create or replace function public.opr_txeqvc(text, varchar)
returns boolean as
$$
select rtrim($1)=rtrim($2)
$$
language sql immutable;
create operator public.= (leftarg = text, rightarg = varchar, procedure =
public.opr_txeqvc, commutator = =, negator = <>, restrict = eqsel, join =
eqjoinsel, hashes, merges);
select 'aa'::text = 'aa '::varchar; -- returns true
drop operator if exists public.= (text, varchar);

select 'aa'::text = 'aa '::text; -- returns false
create or replace function public.opr_txeqtx(text, text)
returns boolean as
$$
-- select rtrim($1)=rtrim($2);
select true;
$$
language sql immutable;
create operator public.= (leftarg = text, rightarg = text, procedure =
public.opr_txeqtx, commutator = =, negator = <>, restrict = eqsel, join =
eqjoinsel, hashes, merges);
select 'aa'::text = 'aa '::text; -- ALWAYS RETURNS FALSE!
drop operator if exists public.= (text, text);