From this answer in 2012 underdark stated:
BUT you won't be able to have curved labels anymore if you move/rotate the labels manually, as far as I know.
It's now 2016, and I noticed that I can enable the
Curved radio button and specify coordinates for my label (see below). However when I specify these coordinates, my label is no longer curved.
I want to specify a particular orientation for curved label around a circular buffer (which I've converted to a polyline), is there a way to do this?