>A main feature I'm missing in almost all open source weblog systems is, what is called, 'threaded comments' or 'threaded discussions'. This is the term I've come across today. We here are all used to it. It is the way threads are commented on the UT. The distinct fact is that comments are made to comments rather than to the main message. Only one of the packages I tested has it: Serenpidity.
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>What also strikes me is that the way it is implemented here is, in my eyes, superior in several aspects. Already displayed messages are not displayed again, thus keeping the list of messages short. The comments can be collapsed, thus keeping it compact. The comment and the list are in separate frames.

A threaded environment is not something that is user friend for most of today's Internet users. This is why most of the discussion boards will have this drop down list of the entire thread. Note that in many places they use the same software so it is the way it works. I like the ability to have it both and the ability to only get what's new since your last login which is something that seems to miss in most of those software even after a few years of being used in production.