Something has changed with suggested topics. Currently, on Meta, I see this:
Note that there are 14 new topics, but only one is shown. This behavior is sticky: If I go to that topic, I’ll see the next new topic on top of the list, but the rest are read topics.
It appears that the new rules are that topics from the same category, even fully read ones, are favored over new topics from a different category, except in the first slot.
Was this an intentional change?