How does execCommand "insertBrOnReturn" work?

I came across this answer but didn't like how in Chrome if your cursor is at the beginning of a paragraph it adds two breaks. Changing the second <br> to \u200C makes Chrome work perfectly, not so much for Safari.

document.execCommand("insertHTML", false, "<br>\u200C");

What is \u200c? Not sure. Found it referenced here.

Dealing with line Breaks on contentEditable DIV

insertBrOnReturn is a Mozilla specific command, Chrome doesn't support it. You can test that with:

 document.queryCommandSupported('insertBrOnReturn')

jsFiddle here, it alert true in Firefox, but false in Chrome.

If you want to insert <br> only, try:

document.execCommand('insertHTML', false, '<br><br>');

Also, check this: Prevent contenteditable adding <div> on ENTER - Chrome