g2 an option on every thread to "Hide Discussion"
It is possible but if you ignore a discussion it will only remove it from the discussion view. If you have the category view as your default view this won't work.
g2 a way to view hidden discussions such that you could undo any hide
Open any category view from the side menu and you should see all the discussions for that category even if you ignored some. You can tell they are ignored because there is a crossed out eye on the discussion icon. If you want to you can "Unignore"
Hope this helps!