I still have the first post Hello World! with its comment. This post and comment behaves correct, so at some point the settings were OK.
Now in my category "At Home" I have a post called Vacation and it has 5 comments. When I browse the posts in this category "At Home" the post Vacation shows all the 5 comments below the post. This is not how I want it. I want it only to show Comments (5). So in order to view the comments one should have to click either the link Comments(5) or the post heading Vacation.
Basically, I want it back like it was when I first installed WP.