I set up a board with this format, (threaded) on a website I'm setting up. This board software is called 'tetra board bbs'. I also like the other format (non threaded) and set up 4 different forum software platforms for testing purposes , one of them being 'V-Bulletin' like Sailnet. The 2 formats are completely different in how they work. This threaded one is great for a conversonational board, the other ones are more topic oriented.
If the community is small I think this style works well. Once the community of posters gets large it doesn't work as well. After a month I still don't know which format to use.
Personally, I get tunnel vision on all the other formats.