Some purist will even be disapoined if they hook a carp (sorry) anywhere other that in the bottom lip, so i think outside of the mouth is well off limits!...
Fishing is done for no-one elses benifit than their own if you catch a fish and your happy with the way you caught it, fine.
I just put foul hooked fish back in carefully and forget about them, with (hopefully) a lifetime left to fish in, i'm not gonna worry about not quiet upping my PB, when i know i will come back and do it sometime.
Graham's article in CF comments on the big fish or bust scenario, and i tend to agree with him, i get my pleasure from catching fish of any size, as long as it's done fair and square!.
Any one remember the article last year about the angler who finally admitted that the "record Fish" he caught (cant remember the species), was in fact found dead in the margins?.. he realised after several years, after recieving cash prizes, bait offers,etc, that he was only really being fraudulant to himself!. same with a foul hooked fish as far as i'm concerned!