I use it if something makes me laugh, almost exclusively. I rarely ever use it to mock someone, because comments that deserve it are rare and usually designed to provoke that exact feeling/reaction. I'm not here to please anyone like that, but sometimes my snarkiness gets the best of me, you know. I'm not perfect.
Edited to add: I would never mock someone's misfortune. It's mostly political stuff that triggers me... so I try to avoid it.
