I posted a comment on Atom the other day, and Gordon made a few comments. I've made changes to BottomFeeder to handle Atom feeds; there was a bug related to changes from 0.1 to 0.2 that I had missed. I fixed all the server side validation issues as well. However, that leaves my question about relevance hanging. Here's the problem, as I see it. There are tons of RSS feeds out there - I see vitually no Atom feeds. I'm sure they exist, but I'm not finding them. Heck, look at the feeds page on Sam Ruby's site - no Atom links listed. There's another issue as well - there are scads of RSS modules, many of them very useful (embedded comments and the commentAPI in particular). Can you use these modules in Atom? I don't know, maybe you can - but the point is, it's not clear (at least to me).
On the posting side, the invention of a new authentication mechanism just seems wrong to me. HTTP has an authentication mechanism, it should be used. As to people not controlling sites - well heck, then how do they add support for this new mechanism on the server side? The site controller has to add it. If they can do that, they can darn well turn on authentication. To my mind, inventing a new authentication mechanism is just silly. Use what's there and move on.