User cards work when the cursor hovers on a shaded user's avatar. (i.e. user with the Established User privilege who filled their About Me section.)
I would prefer it appeared when hovering over the user's display name too. This is because I tend to click the name to reach the user profile. The user card should act like a preview for the profile I'm considering visiting.
I propose we add this functionality to the names, as well as the avatars.