I think most people who use it are just scared from the uneducated downvotes/ backlash and I think it just ruins the sarcasm.
I started to avoid using it on other social media as it seems kind of dumb.
My opinion for it on Lemmy is mostly the same but it might work better here if Lemmy had a sarcasm tag instead(the same way NSFW tag work)of /s to signal the sarcasm instead.
Instead of typing /NSFW, Why do we tag NSFW?
There is no difference. The end result is exactly the same.
Unless you want the ability to utilize the tags. For example : never show sarcasm posts/comments
Or
Only show sarcasm posts/comments
Then there would be a difference