Finally I've had time to look how Community Server 2007 handles the main site's RSS feed, which you cannot setup in an RSS proxy (like Feedburner).
The problem is not configuring a new RSS for the whole site in Feedburner (that can be done in seconds), but how to maintain current subscriptions without forcing them to re-syndicate the new url.
Sadly, the only solution (not requiring heavy changes to CS) relies on a simple HTTP 301 redirect to the feedburner RSS and modifying the SiteUrls.config file to point to the redirection file.
Anyway, it's already done so if you want, you can change the old RSS url (https://kartones.net/blogs/MainFeed.aspx) to the new one (http://feeds2.feedburner.com/KartonesNet), or keep the old one, it should work too ;)
We are finally able to gather RSS traffic and stats from the main feed!
How to change it
First, I edited my /Themes/xxxx/Blogs/blogs.Master page, removed the CS-generated RSS links and added my own:
<li class="CommonSidebarRssListItem">
<a href="http://feeds2.feedburner.com/KartonesNet">RSS Syndication</a>
</li>
Then, I edited the /blogs/MainFeed.aspx file and added a 301 redirection:
<script runat="server">
private void Page_Load(object sender, System.EventArgs e)
{
Response.Status = "301 Moved Permanently";
Response.AddHeader("Location", "http://feeds2.feedburner.com/KartonesNet");
}
</script>
And finally, I modified the SiteUrls.config file to point all subgroup feeds to the main one. I want this feature disabled, at least for now, but you could modify the MainFeed.aspx to redirect to different feedburner feeds depending on the chosen group with small changes to the siteurls filters.
<url name = "blog_aggregate_Syndication_default" path = "MainFeed.aspx" />
<url name = "blog_aggregate_Syndication" path = "MainFeed.aspx?GroupID={0}^Type={1}" pattern = "MainFeed.aspx" vanity = "MainFeed.aspx" />
<url name = "blog_aggregate_Syndication_tags" path = "MainFeed.aspx?GroupID={0}^Tags={1}" pattern = "MainFeed.aspx" vanity = "MainFeed.aspx" />
<url name = "blog_aggregate_Syndication_tags_unfiltered" path = "MainFeed.aspx?GroupID={0}^Tags={1}" pattern = "RawMainFeed.aspx" vanity = "MainFeed.aspx" />