I've never paid enough attention when I'm using the "mark as read" function. But I have noticed that sometimes it reads "Mark forum as read", and other times "Mark all topics as read". That may be the difference between just marking the threads on one forum board as read, and marking any topic anywhere as read.
For example. I looked in on the gear section today. Read a couple of threads, then wanted to mark the rest as read. But just on that board. I clicked on "Mark all topics as read"...and everything, everywhere got marked as read.
BTW, one reason I like to sign in before reading is that gives you the "new posts" indicator for each section, on the forum landing page, and also shows which threads have new activity, when viewing a particular board. When I'm trying to make the most of my visits here, that can be really handy.
Play like you've worked at it, and don't worry about sounding like your influences. You can't cheat on them, or your practice, anyway. If you've worked hard at your skill, your audience will know it.