The book I am reading is "Alexander Pope: The Major Works," published by Oxford World's Classics, with introduction and notes by Pat Rogers.
I looked everywhere in the book but the obvious section near the beginning titled "Note on the text". This section explains
> Notes at the end are signalled by a degree sign in the text.
So the degree sign has nothing to do with poetry but rather is the notation used by Pat Rogers to indicate commentary given at the end of the book.