Nope. You would not believe how much we labor over these things and have discussed this very issue. "Bullshit" is neither a PG-13 vulgarity nor is it a reference to a poster. It is, decidedly, a comment about the content of the post to which it is a response. LMAO or LMFAO is not about the content of the post. It is, as you state, a mocking "get real" or "you can't be serious", making it about the poster and thus, off topic.
Totally different story if "LMAO" is posted as a reply to a humorous message.
It doesn't look like I'll be running out of things to do any time soon.