"server = 1" enables the server mode in Bitcoin Core, in other words you can run the GUI client and also send JSON-RPC commands to it. If you don't use "server = 1" and you still want to execute JSON-RPC commands then have to choose between the GUI client (Bitcoin Core) and bitcoind, as they cannot run concurrently for the same configuration. It makes no difference if applied as-is to bitcoind.
Do I understand correctly that I only need to set server=1 if I want to run bitcoin-Qt?
I will not be running bitcoin-Qt.
I want to run bitcoind and I want it to accept JSON-RPC commands from p2pool.
Do I set server=1 or server=0 or leave it commented out?