This can be reproduced consistently. You just have to be very fast. This is how I can reproduce it:
- Click on a member to bring up their member card.
- Immediately afterward, click on another member to bring up their member card.
- The second member's member card will not be surrounded by an overlay mask color. Additionally, clicking outside of the member card will not close it like it normally does. You have to explicitly click on the X.
For best results, do this on the forum list with people right next to each other. In my case, before I even clicked on Valhalla's avatar under People You Follow (the one with the "no avatar" avatar), I was already moving my cursor toward and immediately clicked Jon's avatar within a split of a second of clicking Valhalla's avatar.