I was idly wondering today, and this is where it got me...!

In chemical days, depending on the thickness of film emulsion, (over)exposure of the film could "spread" the edge boundaries of the image being captured, e.g. a light area next to a dark may have a softened edge (reduced acutance).

Is it possible for the same to happen in digital?

I presume it won't happen at the physical level (crossover between sensor pixels), although you never know!

(For a single-shot back,) does interpolation of each pixel happen only once? Would an overblown highlight affect the value of next-door pixels? If interpolation is a "looped" affair, could this then spread?

I appreciate that this is probably not much of a problem, as sharpening will just increase the edge contrast again anyway, but I was curious.

Any ideas?