The /S is known as the sarcasm switch. When you are typing a post use it at the end of your post so people know you are actually being sarcastic.

Another version of :S, but cuter.
An emoticon to show confusion.

Shoot, Shovel, Shut up

As in, to kill someone, bury their body, and not say anything about it

S&S, Signed & Shared. Petitions that are on Facebook ask you to sign and share, so if you signed and shared the petition on the post, you can type S&S for Signed & Shared in the comments section. Comments: S&S, S&S, Signed & Shared, signed and shared

If you're sent S on snapchat, they are sending streaks. To get streaks to work, send an S every day back and forth. If they forget to send their S one day you are welcome to scream at them.

Seen and Acknowledged.

Passive aggressive acronym used to professionally respond to messages on “whatApp.” This is useful because “WhatsApp” does not have the feature where you can “like," “heart," “haha,” or “emphasize" a text the way that you can on iPhone messenger.