[nephanth]

Indicating sarcasm is not necessarily ruining it though. Look at IRL sarcasm, it will generally be accompanied with the right tone of voice and expression / body language that make its presence unequivocal. That doesn’t necessarily ruin it

[Fogest]

It's the same reason why I often throw a emoji on the end of a sentence to a friend. Sometimes the sentence on its own can sound aggressive or hostile and a quick fix for that is a little emoji that can help make sure my tone is clear. I view something like "/s" as being quite similar to this. You're not ruining the sarcasm, but instead ensuring your tone is properly understood.

[hnick]

Written works have had sarcasm, irony, and related forms of wit for as long as they've existed. While people might miss the mark, it doesn't mean we should just give it up as impossible just because we're now writing comments online.

And it probably says more about me than the writer, but I always cringe when I see /s since it seems to be implying "Hey, in case you're a bit slow, this is sarcasm. Glad to help."

Sarcasm is by definition kind of elitist. You get it, and you're in the cool group, or you don't and you go on your way. It's a puzzle to solve. Removing all uncertainty removes its fundamental essence.

[eyelidlessness]

/s is just a wink, you still have to figure out whether the person did really fart and if so how they concealed it. You’re just here farting and calling it higher smelling because you think you’re the only one smelling it.

[marvin]

The very best sarcasm is so perfectly balanced and indistinguishable from the real deal, that it will leave its audience wondering but not missing the potential for sarcasm. Then the person that delivered it will promptly move on, before the audience gets a chance to really think about it.