BUG #2507: Problem using two-phase commit

The following bug has been logged online:

Bug reference: 2507
Logged by: N. Ramirez
Email address: noramirez(at)speedy(dot)com(dot)ar
PostgreSQL version: 8.1.4
Operating system: Linux Suse 9
Description: Problem using two-phase commit
Details:

I do not have an operation as it must be when use the functions to do
2-phase commit

Example create table prueba (a int, b int);
begin;
PREPARE TRANSACTION 'aaaa';
insert into prueba values (1,2);
ROLLBACK PREPARED 'aaaa'; select * from prueba
a b
-----------------------------
1 2
because?
it did not do rollback?
as it is used the method of 2-phase commit?
idem for use of dblink