Why is this it that plural? It's not a noun!

Why is this it that plural? It's not a noun!

It's just that in some occasions (mostly seen in informal occasions, such as Internet chat, etc.), the "'" sign and the letter "I" are omitted and directly followed by "s". For example, this is will be abbreviated to "this's" or "this" is wrong. These words are absolutely impossible to have "plural form". Don't learn this kind of informal writing!