Maybe itâs simply just permanent unconsciousness, as opposed to Impermanent unconsciousness (rebirth/anicca). Perhaps unconsciousness is only seen as bad or unpleasant when youâre conscious, but many people enjoy sleep, or they donât actually enjoy sleep, they just enjoy the moment before sleep when they feel drowsy. So in a way, how you feel about unconsciousness is determined by the emotional state prior to entering unconsciousness. Perhaps when youâve mastered fourth jhana, unconsciousness is seen as extremely pleasant and agreeable.
We can use some deductive reasoning about what parnibanna is like, the main point there is no body, so there are no senses. If there is an âexperienceâ then maybe itâs just the colour white (light, bright mind) instead of black (dark, unconsciousness). Aside from that, there are no thoughts or other sensory input, so you should be ok with a state of white light 24/7
Whether there is any form of raw awareness is up to interpretation, but if there is awareness then itâs not unconsciousness. As in my opinion, awareness is what constitutes a sense of continuity, and the Buddha said that those who enjoy sleeping are like those who are already living like theyâre dead.
To me the deathless means awareness, and death/sleep/unconsciousness means non-awareness.
âIn the case of a monk who has died & passed away, his bodily fabrication has ceased & subsided, verbal fabrication has ceased & subsided, mental fabrication has ceased & subsided, his life force is totally ended, his heat is dissipated, and his faculties are shut down. But in the case of a monk who has attained the cessation of perception & feeling, his bodily fabrication has ceased & subsided, verbal fabrication has ceased & subsided, mental fabrication has ceased & subsided, his life force is not ended, his heat is not dissipated, and his faculties are bright & clear. This is the difference between a monk who has died & passed away and a monk who has attained the cessation of perception & feeling.â[2]
The key point is bright and clear faculties. If there is an eternal citta, then it would have the experience of bright and clear faculties.
So I would conclude that the difference between unconsciousness and parinibbana, if there is one, is probably awareness. Hence Sariputta says in cessation he is aware of one perception ceasing and another one arising.
One perception arose in me and another perception ceased: âThe cessation of continued existence is extinguishment. The cessation of continued existence is extinguishment.â Suppose there was a burning pile of twigs. One flame would arise and another would cease. In the same way, one perception arose in me and another perception ceased: âThe cessation of continued existence is extinguishment. The cessation of continued existence is extinguishment.â At that time I perceived that the cessation of continued existence is extinguishment.â
https://suttacentral.net/an10.7/en/sujato
So perhaps all youâre aware of permanently 24/7 forever is:
"At that time I perceived that the cessation of continued existence is extinguishment.â
That one experience for life. (not for death).
Eitherway, parinibbana is either permanent awareness or permanent non-awareness (unconsciousness), take your pick 