Hello,
The 'Report to moderator' link is indeed based on the Spam deletion block and is not available in core.
In addition, we have added extra functionality to protect moodle.org, as the site is frequently attacked by spammers. For security reasons, we don't have any plans for sharing this custom code in the Plugins directory, sorry!
If you are keen for a 'Report to moderator' feature to be included in core Moodle, please see the guide New feature ideas for what you can do.