I don't think that's grammar, I think it's punctuation. Please correct me if I'm wrong....
See 1a.
Also, it's an English Language joke about how the English language is screwed up.
Definition of grammar
1
a : the study of the classes of words, their inflections (see inflection 3), and their functions and relations in the sentence
b : a study of what is to be preferred and what avoided in inflection (see inflection 3) and syntax (see syntax 1)
2
a : the characteristic system of inflections (see inflection 3) and syntax of a language
b : a system of rules that defines the grammatical structure of a language
3
a : a grammar textbook
b : speech or writing evaluated according to its conformity to grammatical rules <appalled at the bad grammar of college students>
4
: the principles or rules of an art, science, or technique <a grammar of the theater>; also : a set of such principles or rules