How do the events of "A Hunger Artist" match up with the flat, matter-of-fact tone in which it is written?

This is an excellent question. Of course, the point of
view of this challenging short story is third person limited, which helps create the
detached tone that you refer to. From the very start of the story, it is clear that the
tone that is created stresses the normal, factual elements of "fasting" as a form of
art:

During
these last decades the interest in professional fasting has markedly diminished. It used
to pay very well to stage such great performances under one's own management, but today
that is quite impossible. We live in a different world
now.

The story presents
fasting as a now outmoded and anachronistic form of art that is no longer popular.
However, to be taken in by this factual tone would be to ignore the very real element of
humour that lurks behind this detached point of view. Of course, the hunger artist is
presented as a figure of pity, but at the same time we cannot ignore the presence of the
absurd. The notion that fasting is an "art" which is presented as an art form before
admiring spectators is ludicrous. Likewise as we follow the struggle of the hunger
artist to pursue his art to its highest and most purest form, we cannot escape the
feeling that the hunger artist is a bit too self-important and places too much emphasis
on his art. Kafka seems to be asking deep questions about the nature of art and the
fervency with which we lead ourselves into states of artistic
excess.