While I agree with not diagnosing self, 3 people is a small sample of those with a personality disorder that would never consider. There are many with personality disorders that are too busy attempting to manage symptoms that don't even have any reference of the disorder. Others consider, but would never admit it to friends and family-they go through process with T and are still reluctant. This is no different than addictions. How many alcoholics are in denial for some time before accepting that they have addiction. Often it is proposed to them and they deny, but then privately admit with reluctance when more behaviors occur.
Also, I think its important to beware of the name and characteristic. They do change. Borderline was thought to stem from childhood abuse for many years, and the last DSM removed that criteria. Just as we don't want to see things(labels/criteria) in ourselves, we often also do not in our kids. I have racked my brain because my 28 yr old has some very strong BPD traits, but has also been successfully professionally. Big characteristic is "you are either God or the Devil". I never even left her with a babysitter until she was 5 except a child care center with parents coming in and out and don't believe any abuse could have occurred. She was the apple of our eye. Now they come out with changes that state that no trauma need exist, its more the hardwiring of the brain. Again, she really does not fill the criteria fully, but I was looking for problems.