This is not an unfamiliar description and although I'm not sure what you mean by a "quiet" bpd but I do understand the struggles taht you're dealing with. I just dont' think that the assumption of someone being bpd is that they are loud, obnoxious people going around throwing tantrums either. I think it differs with every person.

I think that somewhere I have read that many times males with bpd do tend to quietly suffer more than females as bpd by nature is a disorder whose major traits have to do with emotions, and this, being something that is suppressed more in young boys, they tend to end up living that way later in life, quietly dealing with this "shameful" disorder that affects them in ways they've learned to deem as weakness. Fact is they say there are far more bpd males than we know of and part of this reason is tied to what I've just said. That most males don't even seek help for the same reasons its shameful to admit that they have strong emotions.

It's not a reality that it is anything to be ashamed about but this world does make it difficult to be a man with these traits in us.

Thus, I think your "quiet" in being bpd is explained - at least in my mind. This is just my perspective and by no means am I an expert. Hope it helps though

S4