I feel it definitely matters when it comes to sensitive people. If this is a group you've worked with before and you know someone may react negatively to a note, it's best to start the field in a private email. Example:
I worked for a company for 6 seasons, and I knew the TD and how he reacted to notes. Even notes that were extremely plain and simple, sometimes set him off, even when worded in the most neutral and positive ways. I also knew he was a very stressed out individual, and he had unloaded on me regarding a note in the past, so I had to send a private email. When there was a request from the director regarding the set and the way a door swung, I sent a private email to the PM first, explained the situation, and let him field it with the TD. Once the two of them came to a conclusion, I included the note in the report the following day.
I think it's best, when you have a note that you just don't know how to word positively, and fear that it may cause a tailspin of angst, it's best to email the PM personally for assistance. It's their job to help you as well, especially if you're new to the company, and they should appreciate your want to not upset others and keep a positive work environment. Yes, it creates an extra step in the process, but don't you want a smooth and happy show?
Also, if you have time during breaks, and if you have the luxury of having your shops on site, it's helpful to go talk to your department heads in person. Even if you write your reports in the most neutral and straight forward of fashions, certain people will interpret tones and attacks, even if they aren't there, so sometimes it's best to field these issues face to face.