Communication is how let your partner know that you are accepting of certain things (and not of others). You cannot have acceptance without communication. You cannot have emotional intimacy without communication. You cannot really understand what is going on with yourself or with the other person without communication. Communication isn't more or less important than anything else for an open relationship (or any relationship), it is a component so basic that without it there is nothing. You have to understand what it is you are accepting before you accept it, which involves communication. Or you run into situations like the guy who thought his wife would "settle down." Did she communicate that? Doubtful, he assumed it and "accepted" it without communication as to the reality and now his unhappy. If you aren't communicating, nothing else matters, and if you are communicating, either everything can be worked out, or you can come to an understanding that it isn't ever going to work. A lot of relationships where people are unhappy fall into the latter category but people don't know that because they didn't, or don't know how to, communicate. So if I seem like I constantly harp on the importance of communication, there is a good reason, I think it is essential to everything else even being a reality.