As designed "Mark read" in single forum marks subforums read

[Andrej]

Affected version

2.0 Beta 1

Expected behaviour: Marks only the actual forum as read.

Reproduced here on the Bug Reports [2.x] and Bug Reports [1.x] forums.

A potensial resolution to this is adding a checkbox "Mark also subforums read", but that would go over into a suggestion...

 

[Mike]

A parent forum is considered a super set of any child forums, thus when you mark the parent read, you are saying you want to children (which are a subset of that forum) as read.

Worth noting that 1.x has always worked like this as well.