Just going to point this out... That's not what you wrote in your original post.
but for that you need to open each profile, while if this will be implemented the way described in OP you will be able to do it having a whole list of people infront of you.
for example clan page or org page, so you don't have to find each post / profile to check
That is way more work than searching for the player and seeing if they are online. For that, you will have to make a post, add the tags, and have a working script for an emoticon that can actively refresh itself to find if a player is in game. "Smile codes" are static figures that don't have to pull constantly changing information from somewhere.