Crucible will allow you to go beyond commenting on source code. Iterative reviews, reports and auditing, plugins, JIRA integration, IDE integration, and much more.
Iterative Reviews
Files are always up to date
When files in a review become outdated, Crucible informs you with the File Outdated Menu. You can then easily update the file with one click (Iterative Review).
Review Multiple Revisions
When adding files to a review, you can also review multiple revisions of a file.
Reporting
Plugin Reports
You can create your own report as a plugin and have it appear in the menu. For example, the 'Review Blockers' report that appears in the user interface is actually a plugin, added in to Crucible. You can use this plugin as a basis to create your own custom reports and add them in to Crucible. See the Crucible developer documentation for more.
Using the REST API
With its own API (Application Programming Interface), Crucible is extensible. If you need Crucible to do more than it ships with and you've got programming chops of your own, the API allows you to build extensions to the application to suit your needs.