Can I allow visitors to post and moderators to promote the posts to front page?

I am trying to create a news website like this one:
http://www.bloodyelbow.com/
where users can post news, and moderators can promote them to the front page. The fanposts are in a different place.

Is this possible in MODx? I know that that website is done in Drupal b/c I saw it in a freelancing projects website, but can MODx accomplish the same things?

Deifnitely possible.

usually Ditto is used for listings, and you can add a tag filtering to push the post to the front page. See the Tagging extender in Ditto documentation.

If u need more help, feel free to post.

Sweet, I’ll start experimenting. If there are any problems, I’ll definitely post here.

Is there a way to assign points to a document so that registered users can upvote/downvote? When a post gets enough votes, it gets promoted?

The ditto call is just filtering documents based on the TV value, so if the user votes are stored in a TV you could use that TV as the filter.

As long as the criteria matches you should be good to go...