Bug overview description.
I noticed that in clicking a unread thread at the top of the forum index the system automatically marks all threads that are below that one on the list and have unread comments as read without even being opened..

What part(s) of the site page(s) are affected?
Forum

What is the expected behavior?
Any thread below the opened thread on the list remains highlighted as unread until clicked on and opened

What actual behavior is given instead?
Multiple unread threads, if i click on the top most thread or thread somewhere in the middle it also automatically marks the unread threads below the one clicked on as read.

Time of incident. (If applicable)
unknown, only now noticed

Can you reproduce the bug every time?
yes

What steps did you take to replicated this bug?
-wait for 2 or more threads to become highlighted from new unread replies
-click and open the top most unread thread
-return to forum index

Errors or other messages returned. (If any)
no

PS: stickied threads dont seem to cause this effect.