I have a BDP mother and unfortunately I am a quiet borderline. I have self harmed, had severe substance abuse problems and generally been unhappy, a lot. However, I cover the whole thing up and generally take it out on myself. I can function AOK 99% of the time.
All I can say is, that when you feel a threat, the emotions and crazy come out. People that you feel are fair and non threatening, you do not feel this way.
If someone is messing with you, you literally could kill them. Yet, you could talk to someone else and be totally nice.
NOBODY wants this. Look at the suicide and self harm rate. Borderlines,bad borderlines, are the hardest to deal with.
However, NARCICISTS and SOCIOPATHS are the utter **** of humanity. These people don't work on emotion,but a lack of. They find borderlines to torture. People who look to their needs and their needs alone. Borderlines can feel intense compassion, narcs and sociopaths don't. They know what they are doing.
Sadly, the narc is fashionable these days and boy do narcs score the chicks, If you have come up against one, you will have everything you do and say twisted. They are serial killers, child molesters, mass murderers and rapists. Borderlines are rarely these things,but they are crazy as hell, and can do terrible things in the moment.
Be aware borderline is very different to full on narc or sociopath. The difference is borderlines struggle to control their raging mind, narcs and sociopaths made a choice in childhood to screw over everyone and cause them pain where possible.
Borderline is like being on a crazy train of fear. narcs enjoy torturing people for their amusement, and putting others down at all costs to become the leader or most powerful. If I see this in people, I run a mile. I just need an hour alone to get sane. Narcs are never sane.