I disagree. In verbal sarcasm, there's often an equivalent, where the sarcastic phrase is said with a certain tone, or certain syllables or words are emphasized, to convey the meaning that that statement is sarcastic and not the actual intent of the speaker. That information is lost in written text, and something like /s simply creates a written equivalent. It hardly "ruins" the sarcastic statement when a verbal equivalent might be similarly blatant and the mark to signify sarcastic intent is only read after the rest of the statement anyway.

Just figuring out a sarcastic statement by virtue of that statement being absurd enough as to not possibly be intended seriously, does not work in situations where the statement is presented by itself without other context, and the assumption that "nobody would say that thing unironically" is false, because in such a situation, the sarcastic and non-sarcasic use appear exactly the same.

Further, having no standard for conveying sarcasm unambiguously would mean that someone who really did intend to say something like that unironically could simply hide behind "I was being sarcastic" when called out on it.

In a normal world that would be true. In the timeline we've been locked in since Harambe, the absurd (often horribly and repugnantly absurd) is occuring so many times daily that it's necessary to note whether you're opposing it or adding to it.

Once you realise that most people don't read most of the information you give them, it sort of becomes a secret power. You can hide all sorts of things in a five paragraph email, let alone a full report.

I started offering cash prizes in the middle of reports, to be claimed simply by telling me you'd read that bit. Not a single taker. I stopped writing the reports after that, and no one noticed.

same here, started to see the pattern of people asking questions which had been in the third line of a paragraph they were responding to.

unfortunately new lines are effective in getting people to read even if it is annoying to look at