but why are we anthropomorphising it to such an extreme that its almost insisting that we have an entirely separate entity, with desires and even a sentience of its own?
I think for purposes of the RR technique, this very defined separation allows the addicted person to learn how to stop taking directives from the midbrain in regards to drinking. The I/IT split can be effective without creating nicknames, dressing it up, and building a dollhouse for the damned thing, but you know, I think that often when people have been drinking to the point of near death against their own better judgement for many years, the idea of naming it and killing it has quite a bit of appeal.
I also second reading the threads, but the best understanding would come from reading RR:The New Cure.