Hi Sarah,
After 11 years of practice as a dietitian and 7 years of reading on the subject I am now doing a PhD on a possible expression of gluten intolerance, and the biggest problem we have IMHO is the diagnostic testing (both IgA bloods and biopsy) are fundamentally flawed - hence the reason I have been foolish enough to register for a research degree while working 30(read 45) hours a week for the NHS.
If you want the full spiel on why they are flawed with references, I can provide, but I really do try not to bore people too often!
Broadly I agree with you that no one should do a restricted diet without good evidence, but if there is health improvement on the diet, and worsening of symptoms on even trace contamination, then as long as the diet is balanced, who are we to say they are not intolerant? Our role when we encounter people like this should be ensuring they have checked that there is substantial benefit from the elimination by controlled reintroduction, and ensuring they are getting an appropriate balance of nutrients, particularly calcium, iron and zinc.
I call these "intolerant" people "ducks" - i.e. they waddle and quack, but I don't need to see the webbed feet to say they are ducks. I will spend quite a considerable time in any consultation where someone has eliminated gluten or is considerings so, explaining the pros and cons of doing the GF diet without testing. Often these people have been from pillar to post with doctors saying they are "fine", that they want to try anyway - so it is critical this is done properly.
You might find having a quick read around FODMAP - particularly the paper by Sue Shepherd interesting if you are interested in IBS, Sue by the way is both a dietitian and is coeliac herself, so she is quite interesting to hear if you ever get a chance to hear her speak.
Helen