Everything works as far as I can tell (I don't have a 3-button mouse to test with), but it introduces some changes to design and behavior that we should make sure are desired.

Since this patch changes the markup of the autocomplete suggestion boxes to wrap everything in a link, there is a visual change (all text is now underlined inside):

Is this okay from a design/UX perspective? Since all the text inside the autocomplete box is now a link, as a user I'd expect that clicking would open a new window in a separate tab. But that's not what happens – instead, the "click" event is intercepted by the OOUI widget as a "choose" event. The user can right-click the text inside the box and select "open link in new tab" (I'm assuming the middle-click functionality is basically a shortcut for this), but that's a little more tricky and probably less likely to be used much.

One potential solution would be to keep the link in the markup, but to remove the link styling here – in theory this would allow users to still middle-click or right-click to open a new tab, but we'd otherwise give no indication that anything has changed (and potentially confusing users who are not using this feature).