I always start out by hitting the "New Posts" option. I browse though those that seem interesting and respond once in awhile. I never start on a certain forum. The only time I even think about specific forums is if I'm starting a new post.
When I come back later I like to see who else has commented in the same threads that I did. Latest example is
this thread. I made my response at 5:18 a.m. and left the board. I came back to the boards at around 12:30 p.m. There were two updates to the thread between my response time and the time I came back.
It is my understanding that when I click "New Threads" at 12:30 the thread with the updates should show up for me since "New Threads" isn't just about threads that have been started since my last visit, it is all threads that have had any activity since my last visit. But for whatever reason I don't ever get to see the ones that I post in again unless I physically go search for them using the Search / Advanced Search / User Name: [Zereh] search.
What makes it even stranger is that it does not happen if I
start a thread. Once I start a thread, anyone who posts on it makes it reappear on my "New Posts" list. As it should. This thread was in my "New Posts" list tonight when I made my third visit to the boards today!
Oh, and this isn't new.

It's been like this for ages ~ way before the new skin was released ~ so I'm pretty sure they're unrelated. I just never took the time to post about it before.
I wonder if I should try making a Zereh1 ID and see if it happens there as well. I don't see any option that I can change that would effect the way it works / doesn't work in my User settings but I'd be happy to help you test it out if you'd like.
Thanks for looking into this. =)