I have 126.96.36.199 on my system and I had to find and fix the typos there. You must be talking about a newer version I think.
I agree on your priorities. Didn't want to push you, just wanted to make shure you have a fix for the obvious bugs and rethink the strategy of obsolete categories not to show.
While I also agree on your actual examples with empty categories I did have problems with categories not being shown when they should be shown.
Take your tree example. In version 188.8.131.52 cat3 and sub3-2 would both not be shown (because view_empty_categories=1 was ignored). Thats a problem even with view_empty_categories=0 because the actual display is a pull down list and not a tree. So the pull down list would be as follows:
You see that the user must think both sub3-2-1 and sub3-2-2 are childs of sub3-1 and sub3-1 is a child of cat1 which is all wrong. He also has no clue that everythinig down from sub3-1 belongs to cat3 and not to cat1.
So the user has no chance of understanding the tree behind it.
I think you MUST show both cat3, and sub3-2, because they do have valid child-leaves. Only the the user can understand the hirarchy and the list must look like this:
The only leaves you may hide are cat2, sub2-1 and sub3-2-2-1 because they have no valid downloads as (grand grand...) children and only if view_empty_categories=0
Currently for example cat3, and sub3-2 are not shown which leads to an ununderstandable list for the user.
I agreee that the problem shows up only if view_empty_categories=0, so the hidden field makes sense as long as this topic is not fixed. But the current workaround in the xml did not work because the whole parameter was ignored due to the 2 typos. Hence the system took it always as view_empty_categories=0.
But wait, there is another bad consequence if view_empty_categories=0:
If you start at root and walk through the hirarchy clicking on the icons and names, whenever you click a (sub) category which is missing in the pull down list the root item is hilighted because the actually selected one is not there. That's how you get totally lost and confused with the pull down list and you really don't know where you are any more. In fact, you can't even jump back to the root again from the pull down list because root is already highlited although you are in a sub branche and clicking on root does nothing.
With my fix I was able to use view_empty_categories=1 correctly and that helped me.
Hope I was clear and this might help y'all.