I don't see a good reason for the "dictionary definition" part of the containment procedures to exist. It's a very effective opening from a narrative standpoint, piquing the hell out of my interest; but given that "causal-absent paranoia" seems to be a Foundation-only term, I don't see why it should be mentioned in the public domain at all.
"Feeling of being watched" seems a bit cliché and cheap as a basis for a scip, but I suppose that's the jaded, desensitised SCP addict in me talking.
You've used a lot of "off-tone" language — stuff you wouldn't see in a scientific report. Examples I remember: "as of right now", "luring it in" (on this site, I strongly recommend against using "it" as a pronoun), "injection of a gaseous substance" (plain incorrect use of "injection"), "two things occur"; "adversity" means "a tough situation", and isn't a synonym for "an adverse reaction". And a few grammar errors/offences against my internal style guide, mainly capitalisation (e.g. after colons: what are you, Victorian, lmao, amirite?); also, I'd personally put a minus symbol in the header text of an expanded collapsible. i.e. "+ show" "– hide".
The antisocial/sociopath distinction didn't seem interesting or related to the themes of the underlying anomaly.
You've used a lot of redaction and "we don't know what it looks like". I can't help but see this as lazy writing; there's an infinite number of ways to combine words together to conjure up an image scarier than "we dunno, ooo". Let me put this in a different way: (usually) mystery is a nice breadcrumb trail to a meaty payoff, but it feels dissatisfying to nibble on breadcrumbs all the way through the piece.
The "destruction of all memories" feels tacked on. It doesn't mesh with the other ideas, mostly because you only have that one-off mention and don't develop it.
I'm going to be mean, so apologies in advance: that dialogue is cringeworthy. When was the last time you heard someone say "What is this, a horror movie?" in real life? When was the last time that you said to yourself "What the hell… My head…" when you thought you were completely on your own? You're expecting this guy to narrate every action he takes when you could easily have used some stage directions. A whispered "Fuck…" D-17729 winces and clutches his forehead is more realistic. That lowercase "kill them all" stuff is bad too. Imagine you were transcribing actual audio: what reason would you have to type the words you hear in lowercase?
That last D-class addendum kind of makes sense, but is a bit poorly explained.
Here's what I liked.
You obviously have a good idea of what effect your words will have on a reader. This seems a stupidly basic thing to say, what with it being the foundation of any kind of writing, but you read a lot of people's first attempts on this site and it's obvious they've fallen at that first hurdle. You have the ability to get out of your own head and into your reader's, which is a great skill for writing and hard to teach. I can't offer any specific lines as evidence for this, but it is evidenced by another thing I like:
You've structured the piece really well, one-off, undeveloped throwaway ideas aside. The paragraphs flow smoothly, and you've clearly thought about the order in which to present your information to keep the reader interested and unconfused. That highest-level, macro planning of fiction is hard, so well done for getting that down.
Finally, there are a few lines of flair which show you've got a good grasp of language. "eyes in the back of their mouth" was nice and spooky.
Final thoughts: I can tell you're influenced by the plain ol' creepypasta of this site's early days, which is both a blessing and a curse. On the downside, our current batch of SCP writers are more into the complex, thematic pieces that knowingly subvert tropes etc, so you're not going to get much kudos from them by keeping it old school. On the plus side, it's a welcome break from the artsy-fartsy stuff, and a lot of the audience of this site aren't writers. Also, I think you should think a little harder and more critically about the stuff you write, particularly in terms of whether it's too similar to stuff which has been written before, and whether any particular idea/section is strictly necessary or useful for what you've written.