Let's not forget about the civic duty to call 911 if you suspect that your friend or your neighbor is suicidal. Emergency medicine has experts that can help much more than National Suicide Prevention Lifeline.
What we need to is make it clear that suicide is your right. Treatment should be completely voluntary at all times. I would wager that the possibility of being restrained for days or weeks prevents many people from seeking help that could actually have made a difference.
No, it isn't your civic duty to take the right to suicide away from someone. It's your duty as a friend and a human being to be a non-judgmental ear and shoulder. But in the end you have to respect their rights as an autonomous being.
Emergency visits are not about locking someone away but about figuring out a best treatment. Whether a person will follow the treatment or not that's a different story but at least someone was there for them, to listen, to help, and with means and experience to do it.