Maybe i’ts time to make a counter question:
What for do you need a “hard light” blending node… what’s the wanted effect… or the context… maybe you are better off with using somethgin completly different ?
Because like also for example here:
There is some reference to Adobe… but not real explaination how in photoshop this filter is “defined”…
Also i do especially quotet his:
Ultimately, it is a meaningless blend mode within a raytracing context.
since you also mentioned it in the title of this topic…
What i mean is… maybe the general idea of hard liht is somehow differently interpreted by Adobe… or even the general idea ( https://en.wikipedia.org/wiki/Hard_and_soft_light ??) can be meet better with an 3D rendereing app than with any photo filter ???
Also this…
…is not really… 
accurate…
Or maybe you want somethign maybe more like this:
( the link to www.minimaexpresion.es … comic style filter/ render is still online )
…so maybe the context is more significant tthan the term or get-used-version from any company ??