First, I'd like to clarify something regarding the phrase "It's fine, Eric likes it." These words have been repeatedly used in arguments here, which is why I used them to hint that not everything can be justified or explained away with that phrase. Personally, I don't recall the developer himself ever saying those words, so I wouldn't attribute them to him.Agreed, we will have to wait and see more of the character development before we have any sort of solid understanding on things. Why I prefer the chapters in which the core group are interacting as it gives better group dynamic insights.
As for the "Eric likes it" parts. That is indeed part of the character and maybe a source of the disconnect some have with him? My early thoughts are that Eric does not mind her physical play and acts with others. That is exciting to him. However perhaps he has emotional infidelity boundaries? Her emotionally falling for and giving in to others might be a line for him? Unsure. Many have said here that secrets are the bad thing, but not really sure Eric cares about that either as he has stated that he does not have to know. As time goes on I think we will get a better idea what is meant by that. Is it that he does not have to know details but at least wants to know that something "may or may not" have happened? Or is he fine with being completely in the dark?
Currently it is really about how the readers are judging Vi's actions (And Eric's reactions) and to that I refer the prior statement of it is indeed early in the plot and will have to see it play out more.
Regarding Eric's boundaries, it's obvious that for a couple who have just started their "non-standard" relationship, certain boundaries do exist, but where they end, I don't know. However, it seems to me that neither of them would be particularly thrilled if the other started developing an emotional attachment to someone else. And to be honest, it would be strange to call them a couple if they had no boundaries at all.