Following my earlier post about my woes with Safari’s Hide My Email feature, I have finally tracked down the problem. I had disabled AutoFill, under Safari -> Preferences -> AutoFill, specifically Using information from my contacts. This is from using 1Password which I found rendered this feature in Safari unnecessary for me. I am slowly moving away from using 1Password and so reenabled ‘Using information from my contacts’ and Hide My Email showed its face again.