When creating an actor from the parent class of ‘Spectator pawn’, dragging and dropping the actor from the content browser to the level will not place it in the world. Right clicking → place actor does work though. Tested in 4.14.3 and 4.15.0 and issue occurs in both versions by following steps to reproduce.
Steps to reproduce:
1.) Right click in the content browser → create blueprint class
2.) In the Pick parent class window, open the all classes dropdown and search for spectator pawn
3.) With the new spectator pawn BP created, drag and drop the icon from the content browser into the level viewport.
Notice that no actor is created.