What about "they should not smile at me"? It's technically correct isn't it?
in this sentence, the word "cười" meaning jeer
should be correct in my opinion
Why is không in front of 'nên' here? Seems to mean that the intent is
they should NOT LAUGH--nên không cười" not 'NOT should laugh and the word being negated is cười, not nên.
There's really no difference other than where the language decides to put it's negation.