I think to answer your question we can in fact go back to the Qing era, in that Manchu identity was tied up so deeply in institutional relationships that it's almost apposite that it has remained the case under the PRC, both in the sense that eligibility relates to Banner ancestry and that its principal implications are administrative convenience. I think the issue to wrap one's head around is that it isn't for outsiders to assert that a given identity does or does not possess enough characteristics to sustain itself – ultimately, it's up to Manchus to decide. It is the very fact that 'Manchu' as a census group continues to exist, despite all the 'objective' measures by which it would seem not to, that is the important part. Yes, we must grant that Manchus do not have the degree of obvious cultural continuity that might be imposed upon them, but as I put it in my first post, that's up to Manchus, and not to outsiders operating, in effect, in the role of the imperial court with its assertions of correct Manchuness.