There are several places in the GitLab web interface where, as a user, you can file and report abuse. You can find buttons to file a report in the following sections:

• Comments
• Issues and merge requests
• The profile page of a user (refer to the following screenshot):

When you click the Report abuse button, the following form will appear:

If you click on the Send report button, an administrator will be notified, and he or she will find the abuse report in the Abuse Reports section of the administration pages: