I think you will find varying opinions.
The hermit is also known as the "electric blue hermit". Most people report this crab to be reef safe and an algea lover.
However you should know that ALL crabs are opprotunistic omnivores and will eat anything if they are hungry or just plain feel like killing something. I don't think they (the electric blues) will attack corals per say but may eat your small snails and other crabs, as well as shrimp and benneficial life out of your sandbed.
All in all this guy does seem to be popular along with the Scarlet harmets and blue legs. Others may be able to offer first hand advice, as I have never owned one.