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For those who don't know: when you comment on frassle it's the same as a blog post on your own blog, along with a link that references the item you're responding to. To make commenting easy for people who aren't registered with frassle, we offer a "comment without registering" option where a user can enter a name, website, and email address along with her comment, much like other blog systems.

The difference is that when she submits her comment and personal information, frassle automatically creates a blog in her name. When she comments later on, frassle will notice a cookie in her browser — a little note we've pinned to your computer that says I'm the person in charge of comment blog #312. Using this cookie, we automatically load her next post into the same automatic blog, so that you can see a history of someone's comments even if they're not a registered frassle user. Provided they are using the same browser and that browser supports cookies, all the user's comments will become part of their (automatic) blog.

Later on, if the same user decides to register for real, frassle will seamlessly "upgrade" their comment blog. In other words, their comments will still be there, but now the user will be able to edit them, make new posts that are not comments, change the title of her weblog, etc. This works because the new user registration also looks for the "I'm in charge of comment blog #312" cookie and upgrades that blog rather than creating a new one.

I rather like this design and wonder why other online community systems don't have something similar.