The key point is understanding that whatever you put out on the internet is going into the “public square”, and that no matter what settings you put on it, someone else can still forward it, refer to it, tell someone about it, etc.
The “e” in electronic also stands for “eternal”, “evidence”, and “everyone”.
By your screen name “Future Snake Eater”, I assume you have intentions of going in the military. I will tell you from personal observation that soldiers do get prosecuted for stupid stuff they put up on FB, Twitter, etc.
If there is anyone in the world you don’t want to see something, exercise a little self-control and don’t post it.
Like I tell my kids: all it takes is ONE person in your circle of "friends" to decide to forward a pic or posting of you to somebody outside your "privacy" wall, and it's thereafter "loose in the wild". If it gets into the hands of people who don't like you, or who don't like your opinion, then it WILL get forwarded to your employer, school, etc.
In the world of the Internet, the ONLY private information is that which never leaves the insides of your skull.
On FR, I occasionally post controversial opinions. I consequently try to avoid posting info that would link my online persona to my real-world identity. My wife knows I post to FR, but I don't even tell HER my FR identity.