In every other vanilla command involving player names, you don't need to specify capital letters in the name and it will still work. However this is not the case with Pingspam, so it's a minor inconsistency/annoyance.

Installing the mod clientside alleviates this mostly, but not everybody has access to that luxury.

Btw I figured out how to get rid of the action bar (what I was referring to by "mentions"), don't worry.

Fixed in 1.2.1.