I've seen several posts over time talking about suicide and the feelings of wanting to kill yourself. I have been there myself, I know how it can be both brutally honest and a statement of frustration. 

What I've learned and I think is helpful, but not easy to hear is that we need others to respond appropriately (and we must also respond appropriately) to suicidal thoughts and statements that are made. They must be dealt with immediately, consistently, and without any wiggle room. 

You have two options: either you want to end your life and you really need help, or you will not end your life and are merely expressing yourself. But by expressing yourself in this way you are attention seeking and manipulating the relationships around you. 

Even on reddit, a post exclaiming you want to kill yourself does no good to you as it validates an irrational belief, pushes you towards that action, and triggers those around you that may also struggle. If you want someone to tell you everything is going to be alright, you need to find a healthier way to do so without enabling you or another's harmful thoughts. 

If you, or anyone you know who has bpd threatens suicide, take it seriously. Take every single statement and action as if they meant it, and respond as if you were worried they actually will do it. Make sure your loved ones will double check with you if you meant to say that, and give you a chance to correct your language to something less intense and more honest, or to get the help you need to save your life. 

By doing this, you will resolve a huge part of what makes having close relationships with someone that has BPD difficult and draining and you will vastly improve your life and support system. 

You may also save a life, because honestly there is no way to know if they mean it or not. Which is why any statement about suicide needs to be dealt with directly.