Comment by red_admiral

The first thing I tried is, does middle-click open a new tab properly? Turns out it does, which already puts this site above average compared to a lot of online shops I use, simply for not breaking a standard browser feature!

Ways I've seen it done wrong include middle-click/Control+click not working at all, because the links are some kind of onclick="javascript:" monstrosity, or the link working but some script in the background also redirecting the page on the tab I originally clicked on.

(I can understand some kind of "flow control" during the checkout process to stop you from double-submitting the "place order" request. But not when I'm browsing the products, and sometimes want two tabs open side by side to compare things.)