Not sure if I understand what you mean. But yes that sounds normal if I understand your question.
When I look at the list of posts for a board, the ones I have read show in a reddish or purple color. The unread ones show blue. When reading them they all look the same.
But if you read messages by looking at replies or reading them in batch mode like "next 50" then they won't show as red or purple in the list of posts.
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