Thanks for the feedback. I've adjusted the forum permissions for the archives, which were meant to be hidden and definitely was the last time I tested. But I've found the problem there and resolved that.
With regards to the white space, our main focus here now is to ensure that users don't feel like important information is being left out in the white space. The white space is more a result of widening the forum layout, we moved from around 650px widths on pages to nearly double that on desktops, the reasons why mobile may feel more nice and compact is just because the screen width is much lower.
But we don't think the white space is a result of removing anything? If it is, please let us know.
And we are looking into adding possible forum descriptions on desktop, in order to reduce the feeling of excessive white space on the main forum page.