Scrolling Text Looks Bad
Some general advice on motion graphics / rolling text, i dont know KDEnlive so i dont know how to achieve that in your specific software.


Make scrolling speed fit your framerate. If your framerate is 25fps, the text should scroll at 25 / 50 / 75 / 100 / 125 etc. pixels per frame.
If you are using a progressive scan playback device like a projector or a computer screen, make sure your project is set to be in progressive and not interlaced. If necessary, de-interlace video that was shot interlaced before using it in the project.
Never use fonts or graphics that have lines which are only 1px, if you need to do that, duplicate the layer and put a copy of the graphics with a very soft gaussian blur (1 or 2px blur) in the background.
Put a soft shadow around the font, also very subtle, 1 or 2px dissolved shadow.