Mark up of all message in thread read not working 1st time

Meta
#1

I hope it isn’t just me but I am reading everything in a thread and go to home (tapping gh or mozilla logo - not back) and I am still seeing in blue the thread as If there are still unread messages.
I need to enter again - last message highlights and again gh or logo to get to home. Now, after second time spent on a thread it gets gray…

Is this a bug or as always - a feature?

#2

this seems to wok fine if used in categories not on main page

#3

Links colours means nothing, there is a request to use always blue and avoid grey for visited links, which is confusing. The way Discourse tags an unread topic is a blue circle.