Sometimes when you put things on here you just want to go away and hide when you realise the answer has been staring you in the face all along. ...Anyway, in the interests of the learning curve, in case anyone else runs up against this.....
It's down to me, rather than ImageShack. ...I've been away over the last few days; on the move using UMTS, via a laptop data card for the first time ever. ...It would appear this is compressing downloaded images, although not immediately obvious until it is a photo you are familiar with (a dialup download of the same has just proved the point). ...Anyone who went to the example image in my opening post must have wondered what I was on about because 'Shift+R' is likewise a feature of this program/service and consequently would (presumably) not have been able to reproduce it (!).
I can appreciate the reasons why this is done, but it would have been nice to have been told in the original documentation for the service. ...From August and the switch to HSDPA this card is suppose to bang out up to 1.8meg, as opposed to 0.35 at the moment; whether the compression situation will change from then, we shall see, although the reasons for doing so would remain valid.