This might be worth trying.
I agree with Tim that’s it’s both rather than one or the other, but there’s definitely a problem with gitter dominating and as a result this forum has not got off the ground. So we don’t really have both in practice. A few cross post, but understandably most don’t, and plenty of people are I suspect not aware of the forum because of this.
I think the problem is one of leadership. I think Mitzy made a good start with this, and did a lot to bridge the gap, and at the time more people from Inrupt and the core were popping in here, but that has subsided and the forum has been very quiet as a result. There are a handful of regular posters, and we get new arrivals from time to time but there is not enough to attract them to stay.
I’m sure there are quite a lot of lurkers, so I don’t underestimate the value of the forum. I do think that value could be many times more though, so I think this is important.
I think @aschrijver explains it very well in the post he links below. We are missing the wider reach and different disciplines, we miss out on the building knowledge base, and all those people for whom gitter is a strange uninviting place. I remember when I first arrived there, and people will know I’m not shy online, but it was quite an intimidating process for someone new including me.