I posted something similar to this quite a while back, but no one listened... ah well.
I think we did kill Durandal on Hang Brain. Remember that Durandal gave us a chip containing a compressed version of himself at the end. We have it; we and the Pfhor can't both have it at the same time, so the Pfhor do not have Durandal. I think the reason that we go through Electric Sheep Three is that, although we were successful in destroying Durandal before the Pfhor captured him, the Pfhor captured us afterward. On By Committee, Tycho says that the Enforcers haven't managed to extract it from our brain yet. Eventually they would, and then the Pfhor would have captured Durandal, and the M2 timeline would have played out. I used to think that Hang Brain and By Committee were the same timeline, but I have changed my mind; I think that By Committee is a slightly different timeline where we successfully escape the Pfhor with Tycho's help, and Tfear lets us fight for him instead of just throwing us back into prison, allowing us to eventually get to Strange Aeons.
