Dead things not coming back to life is a given, it doesn't need to be stated in a story.

: : Anyway my point with that is that basing a story in a "fact of
: : life" like that grounds it and humanizes it and gives it more weight.
: : Wanting to help someone and not being able to is relatable. Having someone
: : die and come back to life is not.

: Again, subjective. The "fact of life" is that humans die. The Halo "fact of life"
: is that Smart AIs have always had a lifespan of approximately 7 years.
: The Halo "fact" is that Cortana is not a typical Smart AI. Whether that's
: relevant or not has yet to be determined, but explicit reference to this fact
: is an outstanding question. That's about as far as "the facts" go,
: as far as my understanding.

I suppose it is subjective, but your counter-argument doesn't have anything to do with it being subjective, it's just stating some facts and saying that that something may be relevant to the issue at hand so we can't assume anything-- and despite your statement here, it seems like you're assuming it is relevant, or at the very least you really want it to be relevant.

: And, again, the content of the farewell scene is not admissable (to
: convince me, as explained).

The ship blew up, what more could they reasonably do to have her die? They could use omniscient narration, but they've never used that in the games before, so that's not a reasonable option. (They could use narration from the future, which has shown up once before, but that was an odd case, and I'm not sure what character could deliver it or what point in time they should be speaking from to not disrupt the rest of the story.) They could have had Halo 4 be the last Halo game ever, but that's not reasonable because there's too much demand for them.

: If they do, then I'll be interested in how they do it. I never said
: anything else can't happen, only that I think they're leaning towards a
: different outcome than that. If I'm wrong, that's just fine; I'll be happy
: if they do the story justice, and if I like the story they tell and how.
: Some people however just seem to be already dead-set to hating on the
: possibility of Cortana returning in any form. That, I can't grok.

I don't understand how you can't understand it. I'm pretty sure most people who engage in much fiction (reading, watching, whatever) would say that bringing a character back from the dead cheapens their death and the story elements tied to it, and it lowers the stakes across the board, and it feels contrived, all things that are detrimental to telling an engaging story. To come at it from another angle (really the same angle I tried earlier, that you went on a tangent about in-universe facts from), basing a story in things that are accepted fact in real life gives it a certain weight and relatability that it wouldn't otherwise have. Doing that makes it easier to connect with. That means going against things broadly felt to be fact takes away something from that, and that is why bringing a character back is generally detrimental to telling a story people are satisfied with.