According to this article at University of Toronto, it’s not. From the article:

I’ll agree.

I’m not sure exactly what the “unique linguistic shorthand” is, besides “LOL” or “OMG” or “BRB” (those are ones I use), but you know what, it’s as simple as this: They’re typed, not spoken the way they are written.

Think about it. LOL means “laughing out loud”. In which case, Really, I’m not going to say “LOL”, i’m going to literally laugh out loud. (let’s forget that Sarah, Jennifer Love Hewitt’s character from Party of Five said “LOL” literally to Bailey.) I don’t think I’ve ever said “BRB” either. Although I might have used that in a jokingly manner. But usually if I say that, it will be more along the lines of mimic-ing Arnold as I say (in Arnold’s voice) “I’ll be back.”

I think teachers and parents are underestimating their children’s intelligence. While there are some linguistic shorthand that might be spoken, I often think of those as slang, and as such, should still be ok to use.

What it all Really comes down to is simple. There’s the way you should talk, and there’s the way you Really talk. After high school and college, how many people are Really going to correct your grammar talking in an everyday situation? I think I can count them on one hand. And no, one of them isn’t my 9th grade english teacher.