Currently it is possible to assign values for expanded or condensed spacing for all scripts. This does 
not make sense for cursive scripts though. WriterEngine/EditEngine should then either ignore (even 
better: disallow) it or they should accumulate the expanded space into the locations suggested by 
normal justification method for this script, i.e. into spaces or into the kashida positions.

Please note that the approach suggested in issue 108684 would solve this too. Let 
WriterEngine/EditEngine distribute the target text widths and let the shaping engines do their stuff 
itself instead of micromanaging the logical glyph positions. This approach would result in something 
similar to the third solution mentioned above.

I'll attach a simple sample document showing the problem in Arabic. The problem happens for many 
other scripts too e.g. for Latin text when a cursive font such as a "Schreibschrift" font is selected for 
this text.