App search has tabs for posts, comments, communities, profiles, professionals and articles. In the posts tab, search looks at the title and the text; in the comments tab, only at comment text.
Sort by relevance, featured, most supported, newest or most comments, and filter by period, from the last hour to the last year.
When you tap a comment in the results, you go straight to the post with that comment highlighted. You can clear your search history at any time.