The forum was meant as another way to communicate with the users of MKVToolNix. I had hoped it would also attract some more people that would answer questions and share their knowledge. Unfortunately the only one answering was actually myself. That gave me no advantage over the usual email communication.
A second hope was that people would use search engines and find answers if their question/similar questions have been asked before. However, judging from the emails and forum posts over the time this hope wasn't fulfilled either.
On top of all that the average quality of the questions asked on the forum was worse than those asked by email.
The cost of hosting a forum
I decided that the cost of hosting such a forum was to high for me (and I don't mean money):
the time it takes to set up the software & configure the server for it,
the time it takes me to fight against malicious people (e.g. forum spammers),
the hassle of having to keep up with yet another information source,
the hassle of having to use web-based editors for composing answers instead of my favorite editor (which can be run from my email application),
the danger of running yet another web application: you have to update it constantly in cases of security issues, you have to monitor releases of the application, you have to merge new releases with the changes you've made locally (both to the code in order to fix bugs and to the style sheets)
dealing with some people even lazier than those that contact me by email.
Therefore I've decided to close the forum. All of the FAQ entries have been moved over to this wiki.