Resharper -> Options -> (Code Editing) C# -> Formatting Style -> Line Breaks and Wrapping
There are a lot of settings for line wrapping. The default for Wrap long lines is normally 120 characters. This may be triggering your break since you are set to 80 or Resharper 8.0 may have a newer option for return. The path above is for 7.0, but I believe it is the same or at least similar to 8.0.
The nice is that they show you examples for the changes you make so you don’t have to test it right away.