I haven't seen your signature so I can't really comment? Theres little tell tales in the way the letters are formed as to weather the person that wrote it does so frequently or not. I don't profess to be a handwriting expert but thats my observation of it.
Possible sure, probable no. Isn't it simpler to just move straight to pissed off employee?
I'm not standing up for Maccas, I don't have any affiliations with them, I've never worked for them and I don't particularly like their food, but this kind of slanderous propaganda really gets up my nose.