Other players have account info when you click on your profile. It isn't much, but it's just a bit about you. I can't figure out how to write anything down there.
It's really simple. Just look at this image and follow the steps below:
So first of all, you need to open this screen by clicking on the Profile button (in the green circle). Then, click on the Comment button (in the red square). It's up to you what you will type in! This may not work if you have "Disable chat" in parental control, or, if you are playing Geometry Dash World or the Lite version (i am not sure about that).
I hope this helped, and I also hope I got the point of your question.