T'Pau leveled a gaze at hir. You are male and female ... and neither. 'It' is the proper word. We have no use for semantic games on Vulcan.

At length he [Jean-Pierre-François Guillot-Duhamel] slept the sleep of the just, on the 19th February 1816, aged somewhat less than 86 years old.

For example, friends who are thousands of miles apart can routinely text each other and maintain a sense that they are actually proximic (Baym et al., 2012).

In answer to this question I want to propose that to is in fact always contentful—that it is never mere Case marking, strictly speaking—but that in certain contexts (namely, in V's headed by Dative-Shifting verbs) its grammatical contribution effectively reduces to Case marking and therefore can be suppressed under Passive.