The missing "and" is a tiny grammatical error, whereas the missing "," Someone mentioned is a large grammatical error. Tiny grammatical errors are OK -- languag

The missing "and" is a tiny grammatical error, whereas the missing "," Someone mentioned is a large grammatical error. Tiny grammatical errors are OK -- language grammars change over time because many people start making the same tiny grammatical error until it becomes part of the accepted grammar of the language.