Hi everyone, I've been on the forums for a while (love the theories, even the crackpot ones) and decided to jump in.
I think Honor sacrificed himself in order to lock Odium in the system. He recognized the terrible threat Rayse posed to the Cosmere (see Skai, Aona) and did the Honorable thing and sacrificed himself. If Odium just killed him and splintered his Shard...well it would be difficult for him to create the visions that Dalinar sees. I view these as his "suicide note".
I also view the Oathpact as him going to the Heralds and saying "Look guys, we can't beat him, our only hope is to contain him. How does an eternity of torture and war sound?".
I try to read all the WoB I can, but if I missed or forgot something that refutes this, then sorry. Please let me know if that's the case.
Edit: I forgot to mention that this is very similar to how Preservation contained Ruin, but maybe even more complete (full suicide instead of just partial)
