What is 'Multi-Factioning'?
Multi-Factioning, at least in the case of Roadside Picnic is been a member of two or more different Factions on the Server; EG: Having a Character in DUTY and another in Freedom.
This is not allowed. You may join one Faction. ONE. Loner Clans are excluded from this rule meaning you can have a Character in a Loner Clan and one in the Military assuming they are not directly in conflict with each other.