Version:            (using KDE KDE 3.5.8)
Installed from:    SuSE RPMs

Can you tell the difference between
A
and 
A    

? Well, the latter one has 4 spaces at the end. However both look the same (at the page) and in Klipper history.

Klipper could add some mark (in different color), like
A<
A    <

for marking the end, or substituting each whitespace character with some icon (in different color).