I have so many questions about how write-ins work. Do you have to write the full names of both candidates? Middle names too? Or can you shorten it somehow? What happens if you make a spelling mistake? What if the counter decides to ignore your vote?
Apparently it sounds like you can use rubber stamps in most places. Can you share the same stamp with other voters? Could you leave the stamp in a voting booth for others to use?
My mind always goes back to Lisa Murkowski getting reelected in 2010 as a write-in candidate after being primaries by a Tea Party Republican. I remember them placing a lot of emphasis on people spelling her name right.
I guess the short answer to your question though is that write in rules vary according to each state's election laws.
They do if the candidate has official write-in status, like the map indicates. If the majority writes in a random celebrity who happens to win, it doesnt count if they didn't go through the state's processes.