Re: Would it be possible or feasible to harvest water from approaching comets?

The first thing to say is that comets  are  mostly water - they're 
best described as "dirty snowballs". The water that some scientists 
believe is to be found at the Moon's South Pole, deep within craters that 
never see sunlight, is believed to have been brought there by occasionally 
cometary collisions.

So it would certainly be possible to collect water from comets. The 
problem comes from the feasibility of such a scheme. Comets are small, 
with nuclear diameters of a couple of kilometers at the most, and also 
quite rare. No more than 50 are ever discovered in a year, and few of 
these pass close to the Earth/Moon system. So almost certainly it will 
always prove to be cheaper to bring up water from the Earth, rather than 
go comet chasing!