Today I wanted to submit a bug for Google (XML) Sitemaps Generator for WordPress. WordPress.org offers a Trac Ticket System under http://plugins.trac.wordpress.org. Obviously, a new ticket cannot be submitted anonymously, so you have to log in. But I could not find any hint about how to register for a new account for this system.
Although the pages wordpress.org and plugins.trac.wordpress.org seem to work independently, it turned out that you need to register on wordpress.org. Logging in there does not log you in for the ticket system, but you can use the same account for both systems.
After login, a button “New Ticket” appeared in the menu bar. I chose “google-sitemap-generator” in a drop down menu and finally could submit a new ticket for the desired plugin.