i'm glad you got responses at least.
they should really add a label- fair enough, people are allergic to all sorts of stuff, but the reactions to this aint apparently nice, and because its not something common thats been around for yoinks, many people just aren't aware of the risk.
i can see why they don't though- how many people would just put it back on the shelf after reading something like "adverse reactions to mycoprotein have been reported by some consumers. while apparently uncommon, these reactions can be both unpleasant and potentially dangerous, and may include hives, breathing difficulties, vomiting and GI distress. those with allergic asthma, histamine sensitivity, mould and fungi allergies and/or other allergic conditions should consult with their doctor prior to consuming quorn." ? my guess is quite a few.