I replied in a forum thread and now I am receiving notifications, but the discussion is of no more interest to me: how can I - on the mobile UI - ignore a thread so that I get no more notifications?
If you are receiving notifications, its most likely because you bookmarked the thread. On mobile, you'll see a little star in the upper right corner of the thread on the menu or next to the title on the thread page itself. Tapping the star until its no longer gold should turn off notifications.
For more comprehensive Notification changes:
On the desktop version (which, I know, is not what you asked for) I can go to my Profile ->Settings ->Edit Profile -> Notification Preferences and change everything about what notifications I receive. I'm trying to access the same thing on my Android and I'm not seeing an equivalent for Mobile. Using the [Full Site] option on my phone does let me access all the Notification preferences just like the desktop version.