Before this change, the right navigation panel (Curtain) had info without Hovercard support.
After this change, all fields, like Subscribers, Tags, Referenced Files etc. have Hovercards.
If you meet an UX problem with a specific field with Hovercard, you can disable that specific
Hovercard, calling PHUICurtainObjectRefView::setHovercarded(false).
This is an example, now with Hovercard support: