[pto0239hn]

Motion blur, but different parts of the image would be exposed differently due to the nature of HDR, resulting in an odd look. Imagine instead of a runner, that you're panning from a dark to light scene.

[kuschku]

Not necessarily.

Assume we say an 8-bit image is taken every 0.1 second, if I merge 4 of them, wouldn’t I just get a 10-bit image with 0.4 second shutter time?

Because I essentially just take the RAW image, load them into a 10-bit colorspace, add them up, and then store the image.