An observation about many of the technical forums and thread visibility.

[passel]

... Most of us develop in a variety of languages, and I'd be more inclined to look through one catch-all forum instead of eight separate ones. (Especially when some of the language subforums aren't languages at all, like jQuery!)

I never look through any of the forums.
I click on the "Settings" menu to see if any threads I've posted in (thus subscribed to) are listed and read those first.
Then I click on "New Posts", which will show what has changed in all the forums since I last logged on and that I haven't looked at already.
That gives the "one catch-all forum", and already ordered by latest post first, so seems pretty efficient to me. I never just trawl around except when originally getting familiar with the site.

....Anyway, I bring this up because I personally am deterred from many subforums before I even enter them. For example, when the front page directory says "two threads, five posts" for the Mobile Development code bank, and the last post is a year old, why would I even enter in the first place?

I'm wondering why you thing that is a bad thing? Why you would want the forum rigged so that you would be tricked into looking at post more than a year old because it was lumped together with other old threads in one combined forum.
We have enough people responding to really old posts as it is without trying to encourage it.