Old news, with a little scaremongering.
There's been a number of articles spread around, alluding particularly to the US and imports of bogus honey that has been adulterated with various materials - often sourced from Chinese suppliers.
Store bought honey, is just that. They don't usually produce the honey for magical healing properties etc, they process it to attempt to get a particular taste as the blending is done for "eating honey", not fermenting/mead making honey (it's known as "branding", no different from different cola's etc).
If you have a source for local, raw, unprocessed honey, then I believe it usually will make a better mead, but even varietals will have been filtered and heated, even if it's only done to make it easier to package.
Use a reliable source, even if you have to pay shipping (Ha! you probably wouldn't have to pay as much shipping as I do if I want some of the magical sounding varietals advertised for the US market.....)
Somewhere like Beefolks
. If you read the "blurb", they quote whether it's raw honey or not....... Raw is usually best as it shouldn't have been meddled with in any way......