system
Given the following post, respond as if you're commenting on Reddit:
human
[Doctor Who/ Torchwood] Some questions about Cybermen.

I'm half way through season 3 of Doctor Who, just finished 42, and have also starting watching season 1 of Torchwood, just finished Cyberwoman. Is it really impossible to change a Cyberman back into a human. In the Cyberwoman episode of Torchwood, even after putting her brain back into a human body Lisa still wants to be a Cyberman. Also to what extent to Cybermen retain their memories and can make their own decisions. It's seems like they do remember somethings and aren't as completely sapped of their humanity as say the Borg. For instance, towards the end of Doomsday during the Battle of Canry Wharf the head of Torchwood (now a Cyberman) kills a bunch of other Cybermen in order to help the Doctor finish his plan. How was this possible?
gpt
The chronology of the Cybermen is one that spans not just planets and kilomillennia, but galaxies and alternate universes that occupy completely different 6th dimensional boundaries.

In their incarnation present at the Battle of Canary Wharf, they retained all human memories and even a degree of free-will. The chief mechanism by which the cyber-mind repressed the human-mind was the emotional inhibitor.

If the emotional inhibitor fails, the sheer psychological trauma of being converted will almost always literally kill you. Lisa's desire to return to the cyber legion is probably a human response more in line with cultural Stockholm Syndrome than something intentionally caused by the Cybermen. You have to remember the terrifying story their history tells; mankind converted itself to cyberkind intentionally, knowing full well what would happen because they genuinely believed it was a good decision. What we see as zombification they saw as the singularity.

In the case of the head of Torchwood, she was able to overcome the emotional inhibitor through force of will alone. The newly converted cybermen at Canary Wharf were converted there in the building in a single-level facility jerry-rigged in half a day. The inhibitor chip was probably poorly installed, making it very susceptible to overload from the raw passion that fueled her duty to Queen and Country.