I don't think the divide is so clear. Sure, many stick to one side of the forum or the other, and I agree that there are absolutely specific tools and techniques for things like suspension and disc brakes, but my thought behind a dedicated board as opposed to a thread means that you can pick and choose which topics you find interesting or relevant to your experience to contribute to. Quality non specific tools are useful across all types of bike and be you roadie or mtber, our workspaces look almost identical, We (mostly) use the same polishes, cleaners, lubes, rust removers etc etc.
I know that delving into the mtb side recently has been amazing for my technical knowledge even as a pretty dyed in the wool roadie; there are plenty of great tips that get discussed on both sides and its a shame to miss them by staying in ones favoured bubble (all too easy to do I know)!