There's no break in the illusion when you come across Jason Jones cutouts in Halo 3/ODST either. Not that that's exactly equivalent; Jason Jones cutouts are of course totally noncanonical, whereas the Halo 4 terminal stuffs are potentially "really there" in some sense. But the narrative does not in any way regard their presence to the characters, aside from whatever justification you want to lend on the basis of you having made the Chief bunnyhop around them.

: it's not a direct reference

No, but now you're changing your words. In any case, "reference" was your choice of words; my priginal choice was potentially even less specific, depending on how the word "comment" looks to you.

: I think that was largely just to let players
: know that they should check the terminals on different difficulties, and
: until or unless you check it on multiple difficulties or hear about the
: differences somewhere you don't know what it mean

Well, yeah. Like I said, the game plays around with it; it's seemingly addressed to the characters, and the characters regard its presense, but the difficulty-dependancy is in some respect directed at the player.

The terminals in Halo 3 are very aware of their own presence, the player is helped to be made aware of their presence, and the characters are aware of their presence. They have a metric froodlenutzskyton of presence. The Halo 4 terms are, relatively speaking, pretty much just floating there; heck, they don't even have presence on the game disc. :P