As usual, not listing everything because it would take too long.
Under no circumstances are any instances of RPC-463 to be allowed to speak
Speak is not concise enough. Is 463 allowed to make noises? If not, why not use the term "vocalize"? If 463's allowed to, then how would the Authority know that 463's not speaking in some unknown language? Is only specific languages used to trigger 463?
Access to RPC-463's containment area and Containment Sector A is restricted to Level-4 personnel only, with no exceptions.
I think "with no exceptions" goes without saying.
regardless of possible needed 463-Θ events
Could be worded slightly better. Maybe "… a 365 day time period. This reprimand is not to be overriden/overruled for a 463-Θ event."
463-Θ events are only to be triggered by unanimous vote of the Global Directors.
I see you're trying to avoid using the word "the" two times. I'd do "463-Θ events are only to be activated under a unanimous vote of the Global Directors.
It is unknown the manner of which RPC-463 achieves speech
Speech is only possible if something has intellect, but your following descriptions don't explain the intellect of 463 and focuses on how 463 makes noises. How about "It is unknown the manner of which RPC-463 vocalizes."
When an instance of RPC-463 speaks, a number of things will occur, including alteration of baseline reality.
Probably my second biggest problem with this article. What is "a number of things"? And what does "alteration of baseline reality" mean? Is it a reality bender, where a gun can turn into a banana immediately? You mentioned 463 changes the probability of things later on, but this sentence doesn't quite reflect that.
I also have some problems with the structuring, which is that this article doesn't follow the "oh shit it's breached containment sequence". Provide information on how we contain it now first, over how we used to contain it.
Your current structure for the description is Appearance/Origin/More Origin/