Is it me or is it TR, in thread view posts don’t retain greyed status

Silly me I always read in the thread view this way each post I read turns grey after reading, that way it is easy to see what I have read and what I have not.

Does not seem to be working now after reading a post and returning the post stays blue, cleared all offline content cookies and such but it still leaves me at a loss.

Thoughts, comments and possible answers are welcome, thanks.