.this is an improved visitor panel, which displays the number of messages and reactions until the next promotion (admin.php?user-group-promotions/).
Note: For administrators and moderators, progress is always 100%.
Note 2: The widget is added here admin.php?widgets/
Strictly speaking, this may not be a "bug" or it may be as designed, but it's just a bit awkward. (If this is better suited as a suggestion, then please move it accordingly.) I can only guess this is because the sub-navigation bar wasn't meant to have dropdowns, at least not in XenForo 1.