Is there a new standard for html commenting?

Recently I found that there is, possibly, a new way of commenting in HTML5.

Instead of the typical <!-- --> multi-line commenting I've read about, I noticed that my IDE made a regular <!div > commented out. So I tested it out, and to my surprise Chrome had commented out that tag (just the tag not the contents of the div, but I did have to close the <!/div> tag like this ).

I tested another and it appears that generally putting an exclamation marker in front of the opening of any tag, this symbol <, makes that tag commented out.

Is this actually new? Is it bad practice? It is actually very convenient, but is it practical yet(if not new)?