So Gary Mitchell appears in the last story of the new Star Trek #400 comic where he is shown creating a solar system before some unknown force kills him. This story is intended as a prelude to IDW's upcoming Star Trek ongoing series. Is this compatible with what was established in The Higher Frontier about Gary Mitchell and Elizabeth Dehner having Spectres hiding in their brains and those Spectres becoming supercharged by the barrier, driving them insane in the process? I know it's not compatible with Peter David's explanation in Q-Squared that Gary Mitchell was possessed by Q who was trapped in the barrier at that time. This is because Q left Gary Mitchell's body after his death.
There is no reason to expect tie-ins from different publishers to be compatible with each other. It has never been Star Trek's policy for all tie-ins to attempt to share a common continuity. What continuities have existed have usually been "local," exclusive to a single publisher. However, while I doubt very much that there's any intention of being consistent with THF, I don't see any reason in principle that you couldn't interpret a surviving, still-empowered Gary Mitchell as still sharing his mind with a Spectre without his knowledge. That was the whole idea, after all -- that it looked like innate psionic ability in certain humans, and that the true explanation was only known to a handful of characters. After all, I knew that nobody else would be trying for consistency with my version, so I had to come up with something that would be reconcilable with stories that ignored it.
But doesn't your novel say that the supercharged Spectres would have burned out Mitchell and Dehner if they hadn't been killed? Is there a way they could've survived or been resurrected and kept their power? I'm aware that tie-ins don't have to be consistent with each other, but it's still interesting to know if they can be reconciled.
Oh, you're right. That does seem unlikely. But most anything can be handwaved if you're creative enough. It's just a question of whether it's worth the effort. I'm generally more content to let different interpretations stand on their own than try to cram them together when they don't naturally fit.