Just something I've been thinking about since most of the differences between the two disorders seem behavioural, rather than a fundamental difference in the overarching symptoms or causes. E.g. people with CPTSD show less impulsive and self-destructive behaviour and find it easier to function in relationships than those with BPD.But it's still common to have mood swing, psychotic symptoms, feeling of emptiness etc in both. 

Any thoughts or links to research would be greatly appreciated.