"But it is confusing for new users, so the ability to middle-click paste was briefly removed from GNOME 3.10."
This is inaccurate in two ways.
One, the change was not made because middle-click paste is 'confusing the new users', though that was cited as an *ancillary factor* in subsequent decision. The change was made due to a plan to use middle click for other functions, and backed out because those other functions weren't ready yet.
Two, the change was not, technically, the 'removal' of the ability to middle-click paste. It was only disabled by default. It could be re-enabled with an xsetting, and gnome-tweak-tool has in fact grown an option to turn it on and off now, if you look at a recent version: this was done specifically to make it easy for people who want to use middle-click paste to turn it back on, at the time when it looked like 3.10 would ship with it turned off.