2nd Edit: As soon as I do refresh, the background goes 'dull', the red icon appears, the post count goes up and my name appears.
This is the answer. Your browser is not reconnecting to our site when you just click back so the database is not being pinged to update the thread list and indicators regarding read vs unread. You can also click on today's posts in the top nav on desktop or the lightning bolt on mobile, to get to a freshly loaded version of the today's posts page.