That's why titles made with Kdenlive do not look very professional.

but it is so true :-)

A very big title eg. 120 Points.

Text is WATER. Without kerning it look like

W A TER

big spaces between W and A and A T.

Kerning shrinks that spaces.

There is another prob: big fonts should have much smaller letter spacing

this is not kdenlive fault: font kerning has been added in qt 4.5, and it's on by default
anyway, this is being discussed by developers: http://www.kdenlive.org/mantis/view.php?id=959

p.s.: i know this is an old thread, but there could be someone interested in this as the issue suggests