This debate is full of assumptions about physics and physicalism that are not valid.  For instance, an 'inexplicable' gravity is being incorrectly used as an example of inexplicableness:

SH: "My point was that we are not entitled to say that "How and why do people feel?" is inexplicable in the same sense that "How and why is there gravity?" is inexplicable."

Gravity has mysteries, as does everything, but , as I will argue below it is actually our unwillingness to consider how force and gravity are understood in physics, to ignore physics as 'inexplicable', that makes the 'explanatory gap' into a chasm. I will give a brief description of gravity to show how far it is not inexplicable because, as I will argue later, this is salient to the description of 'feelings'. How gravity works is known at a fairly deep level - whether a physicist hypothesises about quantum gravity or classical gravity he will agree that gravity is due to the existence of four dimensional spacetime.  In spacetime the distance an object travels in time is measured with a clock and the rate at which clocks tick varies with velocity.  A succession of different velocities results in a succession of different rates at which clocks tick so 'acceleration' is a curving path in spacetime . If the rate at which clocks tick varies over a given spatial distance there is a curve in spacetime geometry known as 'acceleration' and manifest as a 'force'.  If the curving spacetime is due to a mass the resulting force is called the 'force of gravity'.

So, how does this description of gravity apply to the description of 'feelings'?  Well, it shows that if we want a physical description of anything we must consider both space and time. If we want a physical description of 'feelings' we must describe where and when these feelings occur or seem to occur.  Do feelings occur for no time at all?  Do they occur in your head or everywhere?  Are they spatially or temporally extended?  These are simple questions.  My answers would be based on examples of feelings. 

Take the feeling evoked by a brief scratch on my arm.  This occurs at the apparent location of my arm in my experience and lasts about 2 seconds. The feeling is arranged in time at the apparent location of the scratching action in that although it seems to be 'present' "the practically cognized present is no knife-edge, but a saddle-back, with a certain breadth of its own" (William James 1890).  Take the feeling evoked by a spoken word, it occurs at the lips of the speaker and the whole word becomes present at that position in my experience.  Take my feeling of 'space'. Space to the left and right and up and down is the existence of many simultaneous things, such as areas of colour or sets of letters on a page.  For me space equals simultaneity within my experience.

Notice how feelings differ from functions, in neuroscience and philosophy functions are a succession of objects as 3D components of spacetime. When we abstractly think of functions we use our time extended feelings to knit together these instantaneous, 3D components and are in danger of fooling ourselves into thinking that this new hybrid of feelings and functions is the same as physical functions - it isnt, physical functions are successions of instantaneous forms, each having gone before the next appears whereas experience is a time extended entity.