The flags:
Accept PB Bans
Accept Cvar Bans
Accept MD5 Bans
send ban commands to the server as soon as a guid is added to the MBi.
The flag Enforce Bans only sends a ban command when a guid that is on the MBi tries to connect to the server.
Bans are only written to the pbbans.dat after a ban command happens when pb_sv_AutoUpdBan is set to 1. If you wish to disable bans being added to the file (and instead being written only into memory and wiped after a PB or server restart), then all you need to do is set the cvar to 0. (Setting can be found in the pbsv.cfg in the PB folder.)
However, since the commands used by PBBans to ban are the same as commands you'd use to ban via rcon, those won't be then added to the pbbans.dat file either. You'd then need to manually add your own bans into the pbbans.dat ;)
If anything stays ununderstood, feel free to ask ^^
~
/*Pisi*/