Can you stand one more question about "Lost"? Deaths in purgatory

In the last season, a couple of characters in “purgatory” were killed…Mikhail and Keamy. Is there any generally accepted theory on this? I suppose it implies that they were so bad that they were unredeemable and died permanently right there in purgatory. But I don’t remember seeing any discussion about it.

I believe Mikhail and Keamy were just incidental characters that were created for the LAX purgatory, they were not part of the group that was actually in purgatory. You can’t die or live in purgatory…you’re just there waiting to pass over.