Handles showing the post screen, loading the post to be modified, and loading any post quoted.
- additionally handles previews of posts.
- uses the Post template and language file, main sub template.
- requires different permissions depending on the actions, but most notably post_new, post_reply_own, and post_reply_any.
- shows options for the editing and posting of calendar events and attachments, as well as the posting of polls.
- accessed from ?action=post.