I have a large variety of hermits and turbo snails (and emerald crabs) all living with my n. wennerae. He ignores them all for the most part. When the smallest hermit was deep in it's shell molting, the mantis took the shell as decoration for his doorstep. I think he got a little peeved that his decor got up and walked away.. but you get the idea.
For everything I've seen and read about mantis, it all comes down to the individual one's personality. I also feel like my hand (well, tong feeding) of the mantis every couple of days keeps him well fed and not looking to hunt his tank mates.