Hadn't heard of Poe's law. I'd say the best sarcasm does contain a lot of truth. Think it used to be that the best sarcasm did leave you wondering a little if it was meant to be sarcasm.

Interesting idea. It can be that everyone has different knowledge base, so everyone has individual interpretations.

For the post in question. I've seen it in real life, so it didn't seem 'extreme' enough to be obviously 'sarcasm'. Though, I could tell it was sarcasm, it was perhaps the good type of sarcasm in that it contained a lot of truth.