Serial Communication letter duplication

So, i was working on something in class, and now whenever I put in this code, the letters of my serial communication seem to be doubling. It doesn't do this on other computers, just mine. I don't think there's a logical reason for it to do this.

Did you change any settings? What’s this tool?

I think it's the web editor / create.

Right. I don’t use it.
Seems some echo mode is on somewhere