A post meant only for friends can end up in front of people you don't know.
Even with a narrow audience setting, if someone who receives it takes a screenshot and posts it elsewhere, you can't stop what follows.
"Just Among Friends" Rarely Holds
An inside joke changes meaning once it leaves the group. The lead-up disappears and only the harsh line remains.
Comments about someone, or teasing within a group, are the most misread once they get out.
Even if you trust the person you sent it to, someone else may look at their phone. Sending to one person isn't the same as one person seeing it.
Decide by Content, Not Settings
Audience settings matter, but don't rely on them alone. Decide by whether you could explain the content if it got out.
If in doubt, say it face to face. Not writing it down is also a choice.
Before posting, ask whether you could explain it if it got out.
At Digital Kodomo BASE, we value not relying on audience settings alone.
Check Why do posts spread even with a narrow audience?