Don't forget that whilst there's a db property related to unread marks, it's at the individual view level (design properties) that you actually determine what, if anything, that view does with unread documents.
For example, view properties / advanced tab determines whether unread marks are used in the view or not. The options for unread marks are "Unread documents only" or "None" or "Standard (compute in hierarchy)".
You can also define unread marks styling for a view—colours, whether to show unread docs in bold, and so on.