Berlyn I understand the problem you describe (which, by the way, it is not a problem to be solved by programming, but by the managers of the forums), but that is not what I am recommending.
What I am recommending is to have pinned topics behave the same as a regular topic (not pinned at top, no first few lines preview), when seeing under "All Discussions."
I am also a strong proponent that a pinned topic is what its name means, pinned. Having it behave as pinned only when they have new messages defeats the entire purpose of pinning it. Again, management of the forum should dictate the amount of pinned topics per category/label, and should not be solved by software.
