pretty much all the ffa servers i play on now have "if saber is off, do not attack!" or something similar in their motd or name. i always follow this rule, unless me and someone else agree to mess around, like having a kicking duel.
if i see anyone not following the rule in one of these servers, i show no mercy. a lot of times a bunch of us who do follow the rules will gang up on them. like one person will grip them while the others hack away.
if i'm on an ffa server that doesn't specify this as a rule, i show other players the same respect they show to me. if they have their saber off and bow, i do the same. if they instantly attack, obviously i'm not going to whine that my saber was off and they had no right to attack me.