[KevinH]

It only checks if an updated version is available, it does not actually update anything. It just lets you know if one exists. Therefore, there is no preference setting to prevent updates as it is just an alert.

As DiapDealer said, if this still bothers you, build you own version without this check if updates exist. Simply remove the UpdateChecker lines in Sigil/src/main.cpp. Or block outgoing connections from Sigil in your firewall.