"John Smith left the conversation."
For some, these words a simple fact of messaging via social media. For others, them's fightin' words. Every since Facebook gave people the power to exit a group message sent to them, they have loomed large over anyone who dares send one. Is it the easy way out of a conversation you didn't want into in the first place or a breach of "netiquette?" Sometimes, it's both. Of course, there isn't anything inherently wrong with vacating a message thread, but because Facebook decides to tell those stragglers left behind that you did leave, it can get a little awkward.
All things being equal, no one should really leave a Facebook conversation shared through a private message. Sure, it's the opt out we all wish we had when coworkers or family members continue to Reply All over and over again, but it is also the Internet version of turning around and walking away in the middle of someone's sentence, something very few of us would do during polite conversation. Frankly, this could all be solved if Facebook would simply remove the notification, but since that isn't an option, there are some guidelines you might want to follow if you are thinking of uninviting yourself from a conversation.