It has to suit the situation and it is not obvious that what fannywhat things are funny.

Sometimes, something funny you thinkyou find funny is boring or rude to other people.

You can also say "Sometimes, something you think is funny is boring or rude to other people" but it is awkward to have two instances of "is" so close to each other.

It depends on other people, so you need to understand the personality of whom you want to make laugh.

Most English speakers won't use "whom" but it's technically correct. "Who" is a subject, while "whom" is an object. That said, your sentence is fine as it was.