Currently the following two full text searches are treated the same:
term1 -terms2
term1 - terms2

Note the space after the hyphen. I'm unsure if this is a bug or by design.

If we look at the industry standard across search engines negated terms generally require the hyphen to be against the term that will be negated, as shown in my first example. This is because users sometimes search queries that contain " - " such as when they copy and paste a song name like:
Michael Jackson - Billie Jean

Users expect "Michael Jackson - Billie Jean" to return the correct results however currently it doesn't.