The safe browsing xpi is apparently only available for download if you are so unfortunate as to live in the USA.

The rest of us can obtain it by visiting

http://labnol.blogspot.com/2005/12/google-provides-phishing-website.html

The Safe Browsing extension seems like a great idea from Google. They have the power to keep it up to date. It has an "Enhanced Protection" option which says it transmits important data to Google about the pages you visit. It also has a report phishing option.

The Blogger comments work %100 for me and in English to boot. Do you have multiple languages installed? Regardless of the default, I've found new software tends to install itself in the last language you set up instead of... ya know.... which language you tell it to use.

David, my OS is German and my IP is German, but both my browser and its default language are set to English... If I could change their chosen language in the Comments extension option, I'd be fine...

Philipp: I wonder why Firefox (or Google?) doesn’t make their extension framework downwards-compatible in new versions.

To persuade people to download new version of their browser, of course.
I know many people that would never upgrade for just security issues, but when a new extension doesn't work... well, then it's another story. :-)

It will be interesting to see how the blogger comments extension evolves. It seems to me that this is another avenue where highly targeted spam can creep in. Effectively, it allows someone to post a free advertisement on any page, anywhere. While there would be too much competition for it to be useful on pages like cnn.com, it would be easy enough to spam lots of secondary pages (such as this very page on Philipp's site). I'm curious to see how much that happens, and if so, whether much of anything can be done about it.