Hah, ignore my questions on the other thread about whether you finished. Obviously you did :)
I'm glad you loved the game. I feel it's a masterpiece on so many levels I don't even know where to begin. I felt like the ending of Infinite was so victorious--like by cutting off that unwanted set of branches from the multiversal tree through sheer will, Booker became a FACT, a constant, without the Comstock variable. I actually believe in a multiverse and am sort of obsessed with trying to be a constant and to value the likely constants in my life across time and space--so I guess you could say for me the game was almost like a religious experience.
Burial at Sea kind of bothered me because I felt like it erased the messages of hope and redemption of Infinite somewhat--Elizabeth seems doomed to repeat the mistakes of her lineage, even though they erased that lineage, etc. And ironically, I think that version of Comstock she murdered was actually on a redemption path toward becoming more like Booker. But I really like what you said here--that in a way, doing so was what erased her and created balance--indeed, her existence did seem to be an anomaly, and it kind of makes sense she'd wipe herself out in that fashion. Still, it would have been nice if our heroes hadn't been consumed by all that self-loathing in the end. For all their flaws, they were remarkable people. Comstock was a monster on an incredible scale--so the fact that Booker managed to beat him means that the good in him towered even higher than his demons, and the same was true for Elizabeth in Infinite. I guess I just wished she'd been able to see that in Burial at Sea. Still, her act in saving Sally did a wonderful job tying full circle to the thematic elements of the first two games and the protection of the innocents as what makes a life worth living--and what makes it worth sacrificing if necessary.