mongodb schema design for blogs

How would you design the schema for a blog-like site with document-based databases (mongodb). The site has the following objects: User, Article, Comment. User can add Comments to Article. Each User can also vote exactly once per Comment.

I want to be able to do these queries efficiently:
1. get Article A, comments on Article A and # of votes per comments
2. get all comments by User B across all articles
3. get all comments User B voted for

My first attempt is to put articles and comments in separate collections and comment can contain a list of users that voted for it. This makes query 1 and 2 simple. And for 3, I added Vote collection which keep tracks of votes by users.

There's some obvious drawback such as duplicating user vote data and query 1 will take two calls to the database. Is there a better approach?

Article {
  "user_id"
}

Comment {
   "user_id",
   "article_id",
   [user_voted],
}

Vote {
    "user_id",
    "comment_id",
}