The thing I find most important about relationship agreements is not the form the agreement takes, but the REASON behind the agreements. This is, in my experience, most especially true with agreements of the form "I do not want to know about _____" or "I do not want to meet _____."
Often, if you ask someone who makes such a rule "Why don't you want to know about X?" the answer you'll get is "I just don't, that's all." To me, that tends to show a lack of communication; people feel the things they feel and want the things they want for a reason.
Now, if a person doesn't want to know about, or doesn't want to know, one of the people involved in a relationship, I think that speaks volumes about his approach to relationship. I've met many such people, of course; it's hard to be active in the poly community without meeting people who have this approach. In every such case in my experience, though, without exception, the *reason* that the person doesn't want to know about or doesn't want to know everyone else always comes down to some unvoiced insecurity, fear, or uncertainty about the relationship.
I've met people who don't want to know a partner's other partner because they believe that keeping this kind of distance will help them preserve their primacy status in enforced, prescriptive primary/secondary relationships. I've met people for whom it is a defensive mechanism; they feel that meeting the other person makes that person more "real," and that triggers insecurities. I've met people for whom it helps create emotional distance that prevents them from having to consider the needs and feelings of that other partner, and who fear that if they have to think about that other partner as a real human being, they will lose their power or status in the relationship.
There are many different forms that a polyamorous relationship can take. But all healthy polyamorous relationships--indeed, all healthy relationships of any kind, polyamorous or monogamous--have certain things in common. Healthy relationships live on open, honest communication; and it is not possible to develop good communication with a person you refuse to be in the same room with.
I can not reconcile "I refuse to meet your other partner, I refuse to know that person, I refuse to talk to that person, and I refuse to be in the same space as that person" with "respect." When person A refuses to speak to person B, it is hard to make a case that A and B have developed good communication, and harder still to argue that A respects B.
I do not necessarily subscribe to the idea that as long as everyone talks about their feelings, it's all good. That is a n ecessary first step, but building successful relationships requires more than just talking about how you feel. It also requires understanding those feelings, looking at them critically, figuring out where they come from, figuring out whether or not they are well-founded, determining if the things you feel match reality, figuring out if those feelings are healthy or unhealthy, and in some cases (such as with fear or insecurity) figuring out what you can do to change them. All of these things start with clarity and honesty, but clarity and honesty by themselves are not enough to guarantee success.
I sometimes feel like a heretic in the poly community. One thing I hear repeated often, especially when issues such as jealousy or insecurity arise, is that "all feelings are valid." I do not believe that's true.
I do believe that all feelings feel genuine to the person who feels them, that feelings are inherently irrational, and that telling a person "Oh, you shouldn't feel X, so just get over it already" is insensitive and unhelpful.
But that doesn't mean that all feelings are valid.
As an extreme example, say that a person has a fear of being kidnapped by flying ninjas. Is this fear valid? It might be genuine, but is it valid? I would say "no, it is not," based on the idea that flying ninjas do not (to my knowledge) exist; the actual odds of anyone save datan0de actually being kidnapped by flying ninjas is nil. So the fear is not "valid" in the sense that the thing being feared simply is not going to happen; the fear serves no purpose and does not reflect reality.
People act the way they do for a reason. People feel the way they do for a reason. If Alice refuses to meet Bob's other lovers, there is a reason. "Oh, I just don't want to, that's just the way I feel" is not a genuine response; it is not a reason.
I say that not all feelings are valid. I also say that it is not enough to be honest about your feelings; there is also, if your goal is to build healthy relationships, the additional component of exploring the why of your feelings, and being honest about that.
There is also the component of recognizing that not all feelings are healthy, and not all feelings should necessarily be catered to.
I realize that "all feelings are valid" is a very validating idea; it makes people feel good about themselves regardless of how irrational or destructive their feelings are.
But not all feelings are valid, and not all emotional responses make for healthy, stable foundations for relationship structures. Sometimes, building healthy, functional relationship structures requires examining one's feelings, and, if they are found to be predicated on ideas that are untrue or unhelpful, changing them.
This is extremely difficult, uncomfortable, awkward work, and it can and likely will take you nose to nose with some of your deepest fears and most sensitive, vulnerable areas. It's not fun. But expressing how you feel is not enough.