Dear Alan,
Providing a "threaded view" is a very important feature in my opinion. This was once one of the main reasons I started using dpreview. Normally I don't like the typical "flat view" of forums, as I have to scroll a lot more to get the relevant information.
In contrast, a threaded mode allows me to choose which branch of a discussion I'd like to follow and which branches I'd like to ignore. It's my No. 1 time saver when participating in online discussions. I'm convinced that this feature alone was one of the success factors of the dpr forums, just as it still is for platforms like Reddit.
And I think it is not just the threaded view itself that is important, but the way it is implemented. Phil Askey got this right from the start and has done a better job than anyone else I've come across on the web in terms of switching between the flat view and the threaded view.
Kind regards, Wulf