Why is “​” being injected into my HTML?

Question

EDIT: You can see the issue here (look in source).

EDIT2: Interesting, it is not an issue in source. Only with the console (Firebug as well).

I have

Answer 1

In my case, symbol "​" did not appear in the code editor MS Code and was visible only in the tab Elements Chrome. It helped to delete the tag after which this symbol appeared and the reprint of this tag was handwritten again, apparently this symbol clung to the ctrl+c / ctrl+v while transferring the code.