What is the difference between approaching the idea 'no-self' and the act to 'depersonalize'?
Depersonalisation as a psychiatric disorder is something traumatic.

Depersonalisation as enlightenment is calming, blissful &amp; liberating; based in the wisdom of seeing the stress &amp; abandoning of attachment &amp; aversion.

It follows the depersonalised enlightened person can act, behave or interact harmoniously in the world. 

The depersonalisation of the enlightened person can be a “secret” only know to them. An external person may never ever suspect or know the enlightened person is depersonalised; let alone enlightened.