While reading articles about copycats & copying which lead to a psychology forum, I came across a few forums discussing how people with borderline & narcissistic personality disorders copy, but for different motives/reasons. They say BPDs mirror others to fill their lack of self or for fear of abandonment, and NPDs copy to outdo people they envy, and be "the best" again.
And of course this is only one type of BPD, not every BPD people are like this. A lot of narcissists I've met however, are kinda like this. But still, correct me if i'm wrong.