I have seen a few cases. I agree that there is significant overlap between bipolar II and trauma/personality pathology, but the key for me is that there is typically very clear interpersonal dysfunction in the latter which is generally not present or less prominent in the former. I will freely admit, though, that coming into our unit or for an ECT evaluation with a historical diagnosis of bipolar II makes me raise an eyebrow and intentionally dig for evidence of a trauma history and focus more on interpersonal functioning than I otherwise would.
Just yesterday I saw a young woman with a diagnosis of "depression with bipolar tendencies" - I don't even know what that means - who described fairly clear episodes of mood elevation lasting a few days (decreased need for sleep, increased energy, subjective mood elevation/irritability). She was sexually assaulted once while in college but otherwise had a pretty benign upbringing, and there was no clear evidence of significant interpersonal dysfunction other than now being extremely hesitant to have sex due to the assault. Her depressive symptoms pre-dated the assault. I ultimately diagnosed her with MDD as the periods of mood elevation didn't quite meet criteria for hypomania, but the combination of very early onset of depression prior to any trauma history, fairly benign childhood (supportive childhood, no history of recurrent trauma, overall successful academically and personally), and a clear, episodic quality to periods of mood elevation that don't quite meet criteria for hypomanic episodes makes me more suspicious of bipolar II.
I do think these cases exist, but I see misdiagnosed trauma symptomatology or personality pathology far more often than genuine bipolar illness.
