Quick Tip: Everyone Can Hear Everything
One of the things that will happen on a show you are on after a while is that you will get comfortable with your crew and you will weirdly start to feel at home on set. Its makes sense because often, while a show is shooting, you will spend more time with the crew than you will with your family. And as a result, it's inevitable that you will get comfortable being there, get to know the people you are working next to all day, and, as it is a normal human emotion even on the easiest of shows, experience frustration from time to time - with specific people, with productions, with the show itself, and beyond.
Here’s my advice to you though : Keep your comments to yourself and if you don't have anything nice to say, don't say anything at all.
The thing about a set is that there are people walking around who you interact with (we will call them actors) who are mic’d all the time. There are plant mics in sets. There are boom poles sitting idle right next to the dolly and today, on almost every set, you may likely have a headset on that may have a hot mic on at all times, or that you may have forgotten to turn off. So assume at all times that anything you say to anyone can be heard by everyone on set and you’ll be ok.
As someone who prides himself with creating relationships with the actors he works with, I will often engage them in conversation, when appropriate and if they are the type of person who would appreciate it, in order to establish that relationship. As a show goes on, those conversations can take all sorts of forms and go almost anywhere. I often flash to Gene Hackman from The Conversation, sitting in a room listening to everything I say, just before I speak. It may seem paranoid but it’s a reality and you never know who may hear you so it’s always better to assume everyone can hear everything and act accordingly.