I believe in general Internet parlance its usage is closest to A, and more rarely C. Obviously, since A could be made about pretty much anything, it is typically restricted to “the concept exists, and is acknowledged by a sufficient number of people” (e.g. “Rule 34 is a thing”).
And since the phrase “is a thing” is acknowledged by many people, we could say that “is a thing” is a thing. Unfortunately, “”is a thing” is a thing” is not yet a thing.
I believe in general Internet parlance its usage is closest to A, and more rarely C. Obviously, since A could be made about pretty much anything, it is typically restricted to “the concept exists, and is acknowledged by a sufficient number of people” (e.g. “Rule 34 is a thing”).
And since the phrase “is a thing” is acknowledged by many people, we could say that “is a thing” is a thing. Unfortunately, “”is a thing” is a thing” is not yet a thing.
“”is a thing” is a thing” is a thing in sense C.