[...] many LW users seem to have a poorly calibrated sarcasm detector. A recent example [...]
I'm not sure I would describe fubarobfusco's comment as sarcastic, and I am not at all convinced that the reason why it was at -2 for a while was that early readers didn't understand that fubarobfusco wasn't literally claiming that typical modern office environments involve being "crammed up against other people with nothing to do" like cattle on a farm. I think it's more likely just that a couple of the first people to see the comment happened not to find it very funny -- which is perfectly consistent with understanding it.
(I did understand it, didn't find it terribly funny, and didn't vote on it in either direction.)
DanielLC's comment indicates he at least didn't get the joke. And if people downvote every time they don't laugh, that's a great way to encourage people to not make jokes.
For example, what would be inappropriately off topic to post to LessWrong discussion about?
I couldn't find an answer in the FAQ. (Perhaps it'd be worth adding one.) The closest I could find was this:
However "rationality" can be interpreted broadly enough that rational discussion of anything would count, and my experience reading LW is compatible with this interpretation being applied by posters. Indeed my experience seems to suggest that practically everything is on topic; political discussion of certain sorts is frowned upon, but not due to being off topic. People often post about things far removed from the topics of interest. And some of these topics are very broad: it seems that a lot of material about self-improvement is acceptable, for instance.