Those orange bars REALLY got your attention haha
Well, I don't believe they're just a gimmick. Sometimes they appear even if there is no light source, it doesn't look like a lens flate. It is also always accompanied by a digital sound effect. It only appears when we look at machines.
My wild guess is that all the machines, or many, are used as recording devices by the Patriot AI.
We see the orange bars in GZ: when in the XOF chopper looking at its control panel, when BB looks at his iDroid, maybe I forget some another one.
We see it in TPP when looking at the generator used to torture people, when we look at the MSX during the truth ending. There's other cases I forget for sure.
There are actual lens flares in the game, and they have a purpose: they tell you when you are being watched.
These orange bars look like fancy lens flares, but make a digital sound and only appear when the camera glances at machines.
I think it's a hint that the machines are watching. Like I said before, Huey says he is innocent, and the mamal pod looks outright evil when it plays recordings condemning Huey. Huey doesn't understand how it could have recorded everything. They are being watched, everyone is under the AI's surveillance from almost anywhere.
In some cases no machines are implicitly present to record what happens, but when Big Boss is hurt the screen starts to burn like film, as if telling us this is being recorded. You can even fast forward time as if you were watching a VHS tape. V's horn is touching his optical nerve. Some posters on MB say "Big Boss is watching".
When other characters suffer or some serious trauma is happening, the screen starts to have orange glitch lines as if a video feed's transmission was being affected.
There's more to this I think, but it's not the first time Kojima toyed with the idea that the game is VR after MGS2. There was once a website for MG, I think it was for some anthology, and it had a memory analysis presentation where you could read character bios by reconstructing their memories.
MGS3 also had the "relive the memories" tagline shown during an early trailer after showing us Snake from MGS2 say we had the magic of the digital age to look at the past, and the Colonel yelling about time paradox if you killed someone like Ocelot, etc. But he isn't even in the game, and the last time we saw him was the AI running the show in MGS2.
It feels like it's always somewhat present, but in this game more than ever.