I didn't called this bug; this is a behavoir which is more than 11 years old.
It makes sense (thats why agree with the correction of that) that the reduction/increasement will also be multiplied by the speed.
I didn't understand that compensation question - you may miss that fact that there is also a decreasement (in hotter places) of spice; this decreasement is also not such high as it should.
So there is not only a "loss" there is also "good" from this feature. (yes i call it feature!)
I will talk with the team about this, maybe we fix this first after the Dark Gate Universe.
So, if the team decide to fix this before that i should fix this before the end of the Dark gate, there will be at least no compensation at all!
regards
Dschibait