When the Right Margin is set at 80 chars, it is drawn at 8*2* chars. This is annoying because I have a 1440x900 screen that I split vertically in to two. This results in two editing areas that are about 80 chars wide. I could see the margin line in both editors when scrolled all the way to the left. Since Netbeans (9.0 beta) is now drawing them at char 8*2*, it is not possible to size those editors so I can see the line in both windows and it is driving me crazy.
This is a first world issue at the moment, but you might find code coming from mac programmers coming in two or more chars too wide in the Netbeans source code.