Honey (a solution of fructose and glucose) forms Hydroxymethylfurfural -- HMF -- when heated. This is the taste of "burnt toast or caramel" and is the result of dehydration of the fructose molecule.
The use of HFCS (also a solution of fructose and glucose) is deprecated (by advocates of natural beekeeping) because of its formation of trace quantities of HMF when heated by the sun. It is indigestible to the bees, they do not possess an enzyme to consume it.
HMF detection is used in food safety testing to test for overheating in handling of honey.
Its likely that the trace volume of wax melter syrup would not prove toxic to a hive (per abundant experience), but this does not mean over-heated honey is "healthy" to bees or humans.
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