Buddha nature is a reality, that some here can testify to. as i see it, buddha nature is Mind, the Self (not self), the Life energy, being, it can manifest in initial stages as emptiness. It is all things... if you are aware of the life within you. you are aware of Buddha nature. One sees that all things are Mind, everything is Life. All of it. there is no separation between viewer and viewed.
my big question is not about the existence of Buddha nature, rather it is how does one really and truly become 'very awake'. how does one access or become vividly aware. since i have not become very awake. i do not consider my enlightenment to be complete... i can however say that this question is not as important as the aphorism... to 'just live'. that life itself is more fundamental than any other teaching and that from the basis of this life, and within it, one is able to attain awareness of suchness (own nature and the nature of all things) and a fully alert (vividly alert) mind. these realizations are not as fundamental as 'just life', they are however still important.
best wishes, Tom.
in any matters of importance. dont rely on me. i may not know what i am talking about. take what i say as mere speculation. i am not ordained. nor do i have a formal training. i do believe though that if i am wrong on any point. there are those on this site who i hope will quickly point out my mistakes.