In reply to Enrico Battocchi.

Yes, Mr Battocchi, I completely understand it! I mean, if users using Jetpack, then they won't need Duplicate Post plugin, as it "duplicates" the feature that is already in Jetpack. But if they are not using Jetpack and want to duplicate posts, it's wiser to install Duplicate Post plugin and not installing Jetpack, because it offers too many features, while users need only one.