In the command to greet one another with a holy kiss, the kiss is of secondary importance. The command is actually to greet one another, and the kiss was simply the way in which that would ordinarily happen. The burden of the command is upon the greeting rather than the kiss. The command is to extend a holy greeting, and there are at least four things from this text that a holy greeting implies.
There is something very distinct about how and why Christians bear the burdens of others in comparison to any other community. The Bible shows us some of the hows and whys that make it uniquely Christian.