If a feathered horse of any breed, is seen stamping, rubbing the rear legs on something or lying down and biting the pasterns and especially if there is discolouration in the feather at the back, it is almost always, because they have something nasty going on under the feather. And yes, unchecked, horses do become stressed and even nasty, being in pain all the time.
I know of one very famous Gypsy stallion in the UK, who has enormously thick feather. He is also known for being extremely nasty in temperament. Very unusual for a Gypsy. I have always thought that his owner would just treat his obvious pastern problems, he'd be a much sweeter horse. This especially, since none of his offspring have ever had a temperament problem.
And this doesn't just apply to Gypsies. All draft and feathered horses are likely to have these problems. Light horses also get it, but most of the time, the owners notice it. Unless you check under feather, most never even know their horses have pastern problems.
And just a note Lauren. Unless he happens to be registered in the Vanner registry, he's a Gypsy Horse/Cob. Very, very few across the world are 'vanners'. This was purely a made-up name, given the breed by one fellow in the US and who started his own registry. The majority of us, would never call these horses 'vanners'. It is not a name seriousl fanciers of the breed and especially Gypsies themselves, like at all.
The word 'vanner' really applied in the old days, to any horse of any breed, which pulled a cart or van in the UK. The men who drove delivery carts/vans, were also known as vanners.