How to make a dividing line in editor?

I was just learning Julia by copying and running others’ codes and for some reason there’s a dividing horizontal line in my editor, which I think is elegant for coding

I don’t understand how and why this line appears and I can’t replicate it myself. Can any friend tell me how to do it?
Many thanks.

It’s not Julia-specific.

What editor are you using? It probably has some meaning there. If I misunderstand, you can copy-paste _ like in the line below, but without # for comment would be a syntax error:


I’m using Atom Juno with Julia1.4.
I notice the line is not a syntax error even without #. And it seems different from your sample

Aha I just figure it out!
Double type # and then input space. The beautiful line would automatically show above!