This answer had the following translation:
You don't have to laugh like that.
(Please, don't laugh at me like that!)
I haven't seen じゃありませんか (じゃないか) used like this before. I would have tried to translate this as "It's ok not to laugh so much, isn't it?"
Firstly, is my translation attempt wrong? Secondly, could someone please give a bit more explanation (and maybe some examples) of how it is used in the above sentence?