From GPLv3 Wiki
A few tips on getting the most out of the commenting system, pending "real" documentation:
In addition to the browser interface, comments can be submitted by email.
The system is designed so that comments must be attached to pieces of text in the existing draft. This is to keep discussion focused on the work at hand, which is to get the license text right.
If you feel like your comment does not apply to any specific existing text, then consider what would need to be added to the license text in order to address your comment. Would the license need an entirely new section? Then attach your comment to the title of the license itself. Would an existing section need a new subsection? Then you could attach your comment to the existing section title. If your comment suggests a change in the overall philosophy in the license, then perhaps text would need to be added to the preamble -- so you could attach your comment to the Preamble title.
You can click on the highlighting on a particular section in order to see the comments pertaining to that section. At the end of each paragraph, there are two characters in light purple: ¶ and →.
- ¶ is a link to that paragraph's #anchor in the license text, so that a browser will jump directly to that point in the document.
- → loads all the comments on the whole section, to spare you from clicking on every different-colored span to load them all individually.
You may also limit the selection of comments that are used to highlight the text, narrowing the display to the comments you are interested in. Click "search" on the statusbar, and enter your search criteria.
To see only the comments on a specific section, choose a section under "Section id is [ - ]"; this lets you choose among the major sections of the license draft. You can also learn the section id by going to "read/say more" for a comment from that section (where the section id is also a link to the query for all comments on that section). You can switch between the license view and the list/threaded view with the "see on license" and "list" links on the status bar.
The RSS feed linked at the top of each page is a feed for the search query that is currently being shown. So you may subscribe to a feed just of comments on section "License Compatibility" or "Licensing of Patents", or even (by hacking the location field) on "licensingpatents.p0.s1". Or "s1" to see all the comments on the first sentences of all paragraphs. Or on comments by a particular user, or comments containing particular text...
The current (daunting-to-install) source is available.