Who adds words in English language dictionary ?

Question

Thats all well and good but bad grammar and spelling actually makes people look like thick,illiterate idiots

Answer 1

Editors I suppose

Answer 2

1. The addition of new words is determined by the dictionary editor(s).

2. As an observation, let me note a couple of errors that you have made...
a) "Thats" should be "That's" which is an abbreviation of "That is", with the apostrophe indicating that a letter has been removed.
b) "makes" should be "make" because there are two nouns making up the subject (which, therefore, is plural):
(i) "bad grammar"
(ii) "spelling".