When in Coma it is not unconditioned, because it has being in coma as condition. Nibbana is not detachment from the world because is not detachment of something from something.
If one is similar to the other in the aspect of detaching from the world, i dont think it can be rightfully be said to be so but maybe in some context.
Nibbana is when suffering or anything that has the quality of suffering, impermanence, uncontrollability and stress does not gain footing.
"Just as an oil lamp burns in dependence on oil & wick; and from the termination of the oil & wick — and from not being provided any other sustenance — it goes out unnourished; in the same way, when sensing a feeling limited to the body, he discerns that 'I am sensing a feeling limited to the body.' When sensing a feeling limited to life, he discerns that 'I am sensing a feeling limited to life.' He discerns that 'With the break-up of the body, after the termination of life, all that is sensed, not being relished, will grow cold right here.'"
In case of a coma that state is brought about by putting a person in coma. One could seemingly say the same about Nibbana as being brought about by doing the 8FNP but that is a fallacy because 8FNP is to cessation of [suffering], not the Arising of something.
Also when someone is in coma, i assume, his faculties will be dull, whilst someone who has entered the cessation will have exceptionally clear faculties.