I just found out that there is an epilogue episode to Lost, named The New Man in Charge, that answers some of the questions left open by the finale, for example
- where the Dharma Initiative packages dropped from the sky come from,
- why there are polar bears on the island,
- what happened to Walt and
- what the purpose of Room 23 was.
The full epilogue can be seen on Youtube:
Apparently Room 23 was used by Dharma to question the captured indigenous population about Jacob and then cause partial amnesia to make them forget about it, so Dharma would not risk a war by violating their truce.
The first time we see Room 23, Alex' friend Karl is being tortured there. ("Not in Portland", 3x07)
In retrospect of this new information about the purpose of Room 23, is there any indication what the Others were hoping to achieve by brainwashing Karl? Why are they trying to erase his memory?