If you're tired of people quoting long posts and having to scroll past it, then this modification is definitely something you want to use.
This template modification will make it possible to resize quote containers and add an "Expand" button to it which can be clicked to view the whole quote.
This modification should work on pretty much all vBulletin 4 versions.
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How to change the height of when the quote should be resized?
Change the 2 occurences of the number "250" in the showthread template to whatever height you want.
How to change the background color of the expander?
Change all occurences of the color "#C2CAD2" in the additional.css template to the hex code of the color you want.