Ok, what does this now mean to me?
Can I get somewhere the updated LibreSource version, where the bug is fixed, and my problems are solved?
Do I need to be a kind of moderator, and watch all the time, when a user creates a new thread, that I configure it, so that the users I want can post messages to it? This would delay my work a bit, since I can not always respond as fast as needed.
I currently solved the problem, by giving all rights to everybody in the forum, which has the disadvantage, that people can delete threads and create other resources uncontrolled. That is what I do not want them to do.