Indeed, coughing may spoil a concert recording whatsoever.  I once heard
a Richter's concert recording of the C major prelude - he plays very
intimately and several well-placed coughs are enough to make me avoid the
recording...  I bet there are even worse coughed recordings.

I also believe some people cough not because they are ill and they do not
take any attempts to suppress the cough and do this with the open mouth.
I have observed several persons who never coughed in the street or when
talking to me, and now they come to my father's concert and utter sparse
but annoying coughs - in the quietest parts, according to the Murphy's
laws...

However, a part of concert-goers do have health problems.  I understand
it but still think the studio recordings are better for many reasons,
including the absence of coughs.

Juozas Rimas Jr (not the one playing)
http://artists.mp3s.com/artists/141/juozas_rimas.html