Your question somehow seems to superimpose onto Buddhism the Hindu Advaitin idea of an illusory self merging into God the Ultimate Reality, except that instead of God, you have Nibbana. Buddhism is different.
Eternalism and annihilationism
There is no eternal self. That would be eternalism. If we associate the self with the mental idea of Nibbana, or eternal ...
There was an intellect that developed to understand the world as it actually is and without a self.
We cannot find a self even among the electrons & photons nor is there an element of 'justice' in molecular chemistry.
When these words have no referents in our most scientifically precise predictive models, is it then not insane to think in those terms?