Posts under #dcc tag are to share the posts of others or the comments of others. You may take any post or a comment from the blockchain to share. How they could know about the tag if they don't know about it.

I mean that we can promote any post or a comment we like from the blockchain. It doesn't matter from what tribe, community or application. The community is build on all hive blockchain. I'm sure you liked so many posts and comments during your curation and creation here. ☺