Please advise if it's common for bipolar disorder to be misdiagnosed as borderline personality disorder?

Sometimes.: Yes, on the surface. Some of the characteristics are similar such as the mood instability, impulsivity, sleep disorder especially the hypomanic states. Unlike the bipolar disorder which have distinct periods of mania and depression lasting at least a week, borderline personality disorder shows a pervasive pattern of instability with extremes of idealization and devaluation.

Borderline: It can happen, unfortunately. Borderline personality disorder already IS a personality disorder, in fact, one of several. Intense fear of abandonment, being manipulative, a tendency to think of people and things in all good or all bad terms, self mutilating behaviors, drug and alcohol abuse, sexual impulsivity, a profoundly disturb sense of self, and extreme emotional volatility.