Marcel, libtiff is very sensible to data type to store in tiff tags. This is why 16 bits color depth is broken in kipi-plugin tiff writer implementation.

I have found this difference with digiKam Dimg::TiffLoader implementation: the width and height value need to be casted from int to uint32 to have a fine tiff encoding.

This is really a weird side effect from libtiff...

So now, kipi-plugins RawConverter is able to export RAW to TIFF in 16 bits color depth.