>Under "Number of messages before the treeview goes dynamic:", I changed the setting to 50. The option doesn't seem to have any effect. The treeview will only go to "dynamic" when there are over 400 messages. Let's agree that 50 may be exaggerated, but I would at least like to test how it works with a lower setting.

You were right. There was a bug in there. I fixed it. Now, under 400 should be in effect as well.