This is an issue about the infrastructure, not libreCMC itself. Unfortunately I couldn't find a better place to report it.
As is, your Gogs instance is sending email notifications that include the email addresses of all subscribers (in the To: field). Thus, each subscriber gets to know the email addresses of all other subscribers.
Please check if you can disable this through Gogs configuration. If not, consider migrating to Gitea, which AFAICT does not have this issue.