Maintenance for the week of April 15:
• [COMPLETE] ESO Store and Account System for maintenance – April 16, 8:00AM EDT (12:00 UTC) - 6:00PM EDT (22:00 UTC)
Didn't even know that was an option before. I can't do it either, but in the pinned threads at the top of the Recent discussions page I get the gear icon to "dismiss" them. I can't do it with any of the other threads though. Also did you notice, they've taken away font colours in signatures, and for comments too I think.
I mainly use IE11. It use to be on the gear icon to the right of your name where notifications, inbox, etc are located. There use to be the mark all posts and mark section there. It is no longer there, but is does now show drafts which it never did before for me.
I did not know the gear icon next to each section had it, never looked. That does work for me. I never mark all read, just sections.