I feel some obligation to reply to this thread because I was the one who tested and determined Etienne Tardiff's overwintered honey reserves were a high percentage honeydew honey. His two (or four?) hives also had very bad dysentery. I encouraged him to get a microscope to test for nosema. I then had photos of his initial microscopic observations emailed to me, which showed one of the highest nosema infestations I've seen to date. 

Whether his hives died of nosema or dysentery or honeydew honey is a matter of conjecture, but they all died and all of those factors were present. 

As to my qualifications, I buy & sell honeydew honey, so I think I've gotten fairly decent at IDing samples of honeydew honey by taste and more importantly, by microscopic analysis. I also do nosema testing for my own bees and for a very large commercial beekeeper. 

I would say at this point with some degree of confidence, based on my own observations and the observations of many beekeepers in Alberta, there is a relationship between honeydew in overwinter reserves and dysentery. But as always, I would encourage us to hold separate in our minds correlation and causation. I don't know why honeydew seems to be correlated to dysentry. I have some suspicions but don't we all. 

I am not, however, convinced there is a link between honeydew and nosema. For example, my bees, displaying the same excessive dysentery symptoms as Etienne's and on similar honeydew wintering reserves, did not have nosema.

I have also observed dysentery, albeit milder cases, when winter stores have high moisture content. However, I'm not satisfied with saying high moisture content CAUSES dysentery anymore than I am with saying honeydew CAUSES dysentery. I suspect there are other intermediate factors causing the dysentery, such as changes in gut bacteria or fungal composition or physiological changes to the gut lining. 

I just didn't want us to confuse dysentery symptoms with nosema and conclude that if dysentery is seen with honeydew reserves the bees must have nosema and the honeydew caused it. 

To summarize more mathematically, according to my observations: 
honeydew correlates to dysentery
honeydew does not correlate to nosema
dysentery does not correlate to nosema
no conclusions regarding what causes what because I don't know the mechanisms involved

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