The BuddyPress @Mentions is it’s system for sending site members a public message, similar to writing on a users wall in Facebook since the mention will turn up in that users activity stream. @Mentions is normally a one to one thing, if you want to have more than one person in your mention then you must include @member1, @member2 etc. In your activity update.
Social Graph Protocol BuddyPress YR is a plugin that aims to improve the information presented to Facebook when BuddyPress pages are shared onto this social media platform, it allows you to edit Meta tags that will be passed to Facebook when your WordPress and BuddyPress Activity pages are shared. This means that you have greater control over how your site is presented.
BuddyPress Greeting Message is a small plugin which posts a greeting message based on the time of day, either over or under the posting form of the Activity page, both in the members profile and the main activity page for the site. For example in the morning it will display Good Morning Username!, followed by a message that you can customise, i.e. “Thanks for logging in, have a great day!”. To the right of the message there is also a picture that gets posted appropriate to the time of day (i.e. sunrise in the morning.