I know cloth shutters and metal ones- the F3 seems to be somewhere in between (?): sort of kinkable, but looks breakable as well.
I *really* like my 'new' F3-non-HP. It feels incredibly tough, tougher than my EOS 1N even.(
If you read the EOS 1N manual it has quite a few precautions about it's shutter curtain stating, "Strongly blowing air onto the curtain may deform or damage it." and "take the picture within 30 seconds after swinging the mirror up to avoid burning the shutter curtain." Nikon F3 uses titanium foil focal plane shutter and does not have the second precaution as the EOS 1N and the rest of the EOS 1 & 3 lineup.
This happens, probably with someone less experienced with loading or when loading IR film in a bag or in the dark. I wouldnt worry unless you see it rub or see marks of rubbing on the raised bumps. Test it by going through the faster speeds with some film.
Unfortunately mine happened when I had the camera hanging around my neck while loading film. I had the back open, camera facing lens down about to load when the film canister slipped from my hand and landed dead centre on the shutter. It looked bad, but everything worked fine, no light leaks or any issues since.