We have run into that a couple of times, meeting a couple who has this ground rule "we don't kiss." Frankly, we don't get it. We like to kiss, and we like to kiss our swapmates quite a bit before moving on to more intimate things such as oral and/or intercourse. It's foreplay for pete's sake, and neither of us is as interested in the other person's body and sex acts as much as we are interested in their minds and personality. Kissing tells you a lot about a person, and I can usually gauge how well my total swing experience is going to be just by trading a few kisses, it seems pretty accurate so far.
We think couples who have this rule have some insecurity issues that have not been fully worked out, because such a rule strikes us as absolutely absured. "Oh, yes, put your tongue inside my vagina while my husband has his cock in your wife's mouth and then later her vagina, but for God sakes, don't either of you kiss either of us, that's just too intimate and special so we like to save that for each other." PLEASE, GIVE US A BREAK...
Love ya all, R&D