Yeah if you put the tags in the content of the posts they will get indexed and search should find them, keep in mind the body of the posts are searched when you search in "posts" so if you are only searching for titles they wont show up.
I want to replace the res.json(user); line 103 by the total unread for the user... but i'm not familiar with nodebb code architecture and don't know how to get this value... i hope somebody can help me^^