On Kik, if your text only shows as "S" (and not "D") does that mean the person blocked you?

S just means you sent it and it's on the server but it hasn't been delivered to whom you sent it. Blocked or not once it's delivered to their device then it goes "D" blocked it will never go to "R" unless they unblock you and read it

No it means your message has been sent but not delivered. Which means that that persons phone is off, or that they're not logged in

Offline

no, it probably means that they have not turned on their phone/app and therefore the message has not even been received in the first place.

S = Sent; D= Delivered