Also, some of the usernames that show up in "users browsing this thread" don't show the hover card when hovered over?e usernames that show up in "users browsing this thread" don't show the hover card when hovered over?
The default user title is pulled from the usergroups table, not the users one. Therefore, Hovercards is blind when it comes to show default user titles.
As for the second issue, if some cards show up and others don’t, it’s probably an issue with anti-CORS strategy adopted to bypass same-site origin for avatars. Hovercards’ adaptive colors feature uses Google’s image cache to grab the avatar’s data, which is then processed and averaged by a JS library. Sometimes Google’s cache is not populated or cannot be reached with certain avatars. Your best bet here would be deactivating adaptive colors, or just wait it out till it works again.
PS: I can add this to my to-do list for the next update, pulling data from the usergroups table sounds like a good idea.