Extension:ReportIncident

The ReportIncident extension allows users to report incidents of harassment and abuse.

Usage
See Help:Extension:ReportIncident for how to use the extension's functionality.

tl;dr : As a logged-in user, visit a user talk page. Then click "Report" in the tools menu, or in the DiscussionTools overflow menu, if DiscussionTools is enabled, and there are topics and comments present on the user talk page.