BUG #4338: Order by seems to trim some characters before sort

The following bug has been logged online:

Bug reference: 4338
Logged by: Domingo Alvarez Duarte
Email address: mingodad(at)gmail(dot)com
PostgreSQL version: 8.2.9
Operating system: linux
Description: Order by seems to trim some characters before sort
Details:

I have a test table:
CREATE TABLE test
(
id serial NOT NULL,
t character varying,
CONSTRAINT test_pkey PRIMARY KEY (id)
)
with tis data retrieved by: select * from test order by 2

4;"---abacate"
3;"arpa"
5;"--- bacate"
1;"dad"
2;"--dad"

I expect the result to be :

5;"--- bacate"
4;"---abacate"
2;"--dad"
3;"arpa"
1;"dad"

It seems that postgresql is issuing a kind of trim on the column value
before sort/compare, because it's ignoring spaces and '-' wich I use
propositally to move some values to front.

Why postgresql is behaving this way ?
I couldn't find an expalanation in the documentation.