In reply to Bruno Piarulli.

Jetpack already has that feature. You can enable post/page/portfolio/testimonial/whatever copying via Jetpack options. So the "Duplicate Post" plugin is like, kinda, the third leg.

That's what I'm talking about; hope mods won't ban this link: https://jetpack.com/support/copy-post-2/

Though if you don't run Jetpack for your website, then it's the whole different story, I agree.