I'd find it useful, but only if all the bottom options were floating at the right:
" Garden.org Homepage
" Back to the top
" Forums List
" Site Talk forum
" Mark as unread
" Watch this thread
" Suggest a Change
But there are some forums that show images in that side space at the right, not sure how it could work with those forums. I do love the images there, and wish it was a part of every forum, not just certain ones. And possibly an option in settings to disable it for those who wouldn't like it.
And I agree the white space is adblocker related. I don't see it either.
Edit: Possibly moving the above suggestion to the left side, and using just simple icons for each category, with a description when mouse-hovering over. Using icons would keep it very narrow and thin. There's enough space for that and it would preserve the images at the right.