Ordo Grammaticus
Ordo Grammaticus is one of the most peculiar branch of The Inquisition, specializing specifically in being the Imperium's pissed off auto-correct. That being said, they don't only underline your mistakes with red; they also like to shove parchment with said mistakes in your mouth and make you write the whole thing all over, which is especially painful with that red pen of theirs stuck firmly in your butt (or eye if you've made REALLY stupid mistake). They justify this sadistic behavior by saying that they pursue the Emperor's own dream of bringing humanity to it's perfection. That being said, they are especially touchy about religious scriptures, official documents and decrees, etc. Another group they particularly dislike are people who imitate ork speech, as they consider this to be a literal rape of Gothic language and old guardsmen argument that ythey are practicing to taunt orks in cmbat doesn't help these days either. Not to mention their down right bulling of lower-class pheasants, some of which don't even speak Gothic and are trying to contribute in their own way.
Forces in service of grammar
As other Ordos, Grammaticus too has it's own lapdogs loyal men at arms to enforce what they believe is will of The Big E himself. Those would be Red Quills and The Erasers. Both are groups of stormtroopers handpicked from Schola Progenium by Grammaticus Inquisitors for showing potential of being meticulous OCD suffering little shits just like their possible future employers and possibly even rise through the ranks among them. This process keeps Ordo supplied with experienced Inquisitors who could gladly spend an entire evening correcting EVERY SINGLE FUCKING SENTENCE YOU SAY (just kidding they usually last like 10 minutes tops before a red pen starts heading towards your anus/eye).
- Red Quills
Red Quills are Inquisitorial bodyguards and essentially walking talking pencil cases (as Inquisitors usually need so much shit that servoskulls can't carry it all). They wear dark red carapace armor and red cloaks earning them a distinct nickname of Crimson Cunts. From two stormtrooper forces mentioned less people are likely to rise from their position in Red Quills than those in The Erasers. The reason for this is that since they got picked straight from the school desks to just yell at uneducated or just downright literate pheasant like some fusion of Gordon Ramsay and your angry English teacher, they are prompted to be a little bit full of themselves have their heads even further up their own asses than Eldar and Red Scorpions combined. And since goals of Grammaticus are to serve The Imperium and it's people in their own unique way they consider them to be mostly unfitting.
- The Erasers
While the SS sturmtropen their colleagues are tasked with following The Inquisitors around and licking their boots, The Erasers are those who actually get shit done. As in: all day every day workhorse tempo kind of getting shit done. They usually wear black armor and prefer lighter variant that offers more mobility in combat and some extra sneakyness. They are The Ordo's extended arm that fights against heretics that spread shitty poorly written fanfic (watch the example only in case of wanting to get purged [1] ) as well as ork-impersonating lower-hive gangsters (ever heard of Necromunda). They also undergo a special training that makes them some quite handy skills that turn them into cross between your standard stormtrooper and Vindicare Assasin. Their job makes them considerably tougher than the previously mentioned force and since they see the worst kind of shit their order can face on daily basis, those that survive can later become fully fledged inquisitors. As for their name. Well that has further meaning than just their employer's love for office tools. Let's just say that some people's existence is so unnecessary and bothering that it's better for them to never exist in the first place. I mean have you heard about those Tzeench cultists, who were spreading some poorly written flyers with daemon summoning instructions? Or that one guy who once called some local recruiting Space Marine Chaplain a SPEEHS MAHREEN? NO? You haven't?...Good.
OK, ok for real now
...if you actually took all of the above seriously, then read up a little more on the subject (although some of it was based on reality). In WH40k community people use the term Ordo Grammaticus for anyone who is essentially a grammar nazi. Although the latter term is more universal, Ordo Grammaticus is becoming more popular as a meme and as a fanfic trope that is starting to spawn new theories (more on that later).
Grammaticus Inquisitors
To identify one in real life you don't have to look further that your daily WH40k Facebook or Twitter page's comments and watch some poor bastard, who probably doesn't even speak English right or got into 40k just recently eat it by every single butthurt who is willing to jump on that brakeless Hatetrain. Of course some may refer as such to people who just edit pages like me, and to people like that I would like to tell to shut THEIR FUCKING HERESY-SPEWING WARP RIFTS THEY CALL THEIR MOUTHS BEFORE I TAKE THIS RED PEN AND...*INTERMISSION*
Theories amd Stories
Fluff-wise there are several theories about things that The Ordo may have stuck their noses into and since not much is known about them and they deny most of that not much you're free to make up your own opinion, just make sure it stays your own if you know what's good for you.
- Ordo Grammaticus vs Commander Boreale
The most notable theory says that, as Commander Mr. Clean was becoming the Jar Jar Binks of Dawn of War, Ordo Grammaticus couldn't just watch as he desecrates the holy name of THE EMPERAH *BLAM* Emperor and spreads his foul manner of "speech" among his own Battle Brothers. The theory even goes as far as that they themselves sent Vance Motherfucking Stubbs to personally fuck his bald shit up and even that Cyrus was the one that provided him with the info to do so, being the sneaky bastard that he is. The theory even goes as far as saying that the loss of those 100 Baneblades was caused by a fucked up order on the Inquisition's part. Though this wasn't confirmed, there are rumors of seeing one of the Ordo's (now former) scribes strolling around his home town blindfolded with something that appeared to be about a dozen pens stuck in his eye sockets WHERE THE FUCK DID YOU HEAR THAT!?...ehm...I mean...Absolutely preposterous.
- Grammaticus Space Marines?
Another theory suggests that Ordo Grammaticus was supposed to get their very own Space Marine force like the other orders. They were supposed to be called The Correctors and were supposed to find all heretical bullshit Lorgar wrote during The Horus Heresy and fight against his forces. There is even a talk of a grand parade where all Grammaticus Inquisitors were supposed to greet their new personal super-soldiers, but a fatal mistake occurred. The banners astartes were holding had all word "Corectors" spelled with only one r. Only other thing we know besides that is that a few days later Magos Biologis recived a cargo of Space Marine geneseed from unknown source. I imagine it took some time to purify it from all the red ink.*BLAM*