Right now, quantities with units are displayed by attaching unit name to the number. While it gives the idea of what is going on, it is somewhat ungrammatical in English (83 kilogramm, 185 centimetre, etc.) and in other languages - i.e. in Russian it's 83 килограмм, 185 сантиметр - instead of the correct "83 килограмма", "185 сантиметров". For some units, the norms are kind of tricky and fluid, and they are not even identical across all units in the same language, but the common theme is that there are grammatical rules on how to do it and we're ignoring them right now.
I think we do have some means to grammatically display numbers with units - for example, number of references is displayed correctly in English and Russian. As I understand, it is done by using certain formats in message strings, and these formats are supported in the code in Language classes. So, I wonder if we should maybe have an (optional) property that defines the same format for units? We could then reuse the same code to display units in proper grammatical way.
Note that this task is not the same as just displaying units in local language - while we can display units now in any language, we display them in an un-grammatical way, ignoring local rules for how one writes numbers with units.