How Do I Hide Specific Forums From the New Posts Feed?
To disable posts from showing in the New Posts page for specific forums, hover over your username in the top right of the main menu. There will be a drop-down box. Look for the link that says "Ignore New Posts." Click it.
Once you're to the Ignore New Posts page, you should see something like this:
Simply check the boxes for all the forums you'd like to ignore in the New Posts feed. In the above screenshot, once I saved the page, it would remove all new posts from Self-Publishing and Electronic Publishing from my New Posts feed.
Enabling this doesn't mean you won't see the forums, merely that posts from these forums won't fill up your New Posts feed.
Click the light blue "Save" button. Your New Posts feed will now ignore all threads for the selected forums.