Originally Posted by
trey harris
The role of +-mentioning someone seems to be confusing people, so let's talk about it.
+-mentions are not the way you talk about someone. They're the way you talk to someone. If you use a +-mention, you're inviting them into the conversation; you add them to the list of people the post is shared with and you notify them that they were mentioned.
This works whether the +-mention is in the body of a post or in a comment, whether the comment is by the original poster or by someone else. If you just want to refer to someone, just type their name without the plus (or @, which works equivalently). If you want to link to their profile, paste the URL of their profile in without +-mentioning them.
Imagine it as a conversation among a few people at a party that everyone you know is at. You can say, "Oh, that reminds me of something John was just saying...." You can raise your voice and make eye contact with John as you say that to invite him to join the conversation. That's +-mentioning John. You can also say, "oh yeah, John had the same thing happen to him," lowering your voice when you say John's name; if he happens to be listening, he can still join in, but you're not explicitly inviting him to join in; that's typing John's name without the plus.
The place where people get surprised by this is when they share a post with a limited set of people, and then a commenter +-mentions someone not in the original share. If the original poster didn't disable resharing, the +-mention will reshare the post to the person being mentioned.
So, the rules to remember:
1. A +-mention is for addressing someone, not for referring to them.
2. If you want to make sure commenters to your post don't inadvertently reshare it further by +-mentioning someone not on the original share list, disable resharing of the post.
Remember, like all privacy controls, you can only be sure when sharing with people you trust not to violate your privacy. Anyone could cut and paste or take a screenshot and share with John, or the entire Internet, no matter what controls you put on the original.