There's a thread over in pgsql-admin
http://www.postgresql.org/message-id/flat/1317404836.812502.1415174912912.JavaMail.yahoo@jws11120.mail.ir2.yahoo.com
suggesting that the server-side autocommit GUC causes more confusion
than it's worth, because newbies think it should reflect the state of
client-side autocommit behavior.
We left that variable in there back in 7.4, on backward-compatibility
grounds that were a bit debatable even then. ISTM that by now we could
just flat-out remove it. Surely no client-side code is still looking
at it.
Thoughts, objections?
regards, tom lane