Lastly. Me? Parelli? Homeopathy?
I know I have said I'd like a bit more science behind it but nowt like running your own case study I spose 
And thus some owners too
You will struggle with the science as it is mostly all mumbo jumbo.
Feed companies use balancing software according the recommendations made by the NRC (2007).
Most of the advice regarding nutrition for horses and the research comes from the 1970s and 1980s or based on theory from experimentation with other mammals or just pure conjecture.
For example - Vitamin A was studied extensively in horses and so feed companies regularly over supplement that. Lysine is one of the most researched essential amino acid - so that is added in most things......
Hence feeding horses is more an art than a science.
You can look at the research being done by Dr Katy Watts on different types of grasses and how non structural carbohydrates (NSCs) affect horses.
http://www.safergrass.org/articles.html
You can look at the recommendations by Dr Kellon on how to rebalance diet.
http://www.drkellon.com/
You can look at the research by Dr Chris Pollitt on laminitis and hooves
http://www.laminitisresearch.org/chrispollitt_publications1.htm
To summarise his work - he induced acute laminitis in Standardbreds and then euthanised them at various stages.
He found that even those horses who were euthanised BEFORE showing any acute symptoms still showed damage to the laminae.
He has concluded that the death of the fibre fermenting bacteria in the hind gut releases toxins, which form enzymes that 'eat' the laminae and cause it to fail.
Why does this happen? We still have no freaking clue......
But it's a start
So how does this relate hooves in terms of diet?
Years ago SOME horses could go barefoot easily and SOME couldn't.
We didn't know why.
Then people started experimenting with diet and started feeding 'Magic Barefoot Powder' (seaweed, linseed and brewer's yeast) rather than commercial mixes.
Horses mostly responded well to this...but some still struggled.
Then people started looking at mineral balancing. Inspired by the dairy industry in the US, who would demand an analysis before parting with cash on hay and then would feed a mineral supplement specially made to fit the hay they'd just bought.
And suddenly those horses who were really difficult to keep barefoot, always needed boots to be ridden, and went footy in the spring - became happy and sound!
As far as I am aware - there is no current scientific evidence to support this...but merely thousands of horse owners all over the world who have found it's helped their horses.
The Cushings and Insulin Resistance Yahoo Group has many files of information about this.
So why does diet mean 'more' to barefoot horses than shod?
Have you noticed that shod hooves are colder and grow slower than barefoot?
I can waffle on about the hoof mechanism and loading versus unloading but in simple terms, as well as lifting the hooves off the floor, the shoes decrease the circulation (and additionally nerve function - but that is currently still a theory) and therefore provide an anaesthetic effect. Inflammation of the laminae will be reduced if blood supply is reduced (which is why cryotherapy is recommended for laminitis cause by a systemic inflammatory disease).
I have witnessed a horse with obvious insulin resistance potter around on sore bare hooves and then stride out sound and happy ten minutes later when shoes are put on. Horse is still insulin resistant and hooves are still sick - but he doesn't feel it any more.
The answer for you (IMO) is that if your horse has an appropriate diet (for them) and has no problems - then the diet doesn't need to change.
But knowing that the hooves are directly affected by diet (as pointed out by the researchers listed above) then it is wise to review if a horse IS having problems - shiny coat or not.
I can appreciate your frustration and that you may feel patronised - but we are giving advice blindly on a forum and that comes with dangers.
You will find the Barefoot Taliban on HHO take the safety and comfort of the other poster's horses very seriously and always give as much advice as possible to make life without shoes painless.
No one wants to hear about lame horses gimping about - so we bang on about diet to try and prevent that because it is simply not necessary for horses to suffer when a simple tinker with diet can help.
Hope this helps