actually it has been done.. I wouldnt recommend a tile saw or dremel.... inland band saw... i've seen them fragged and I've bought one after it was fragged...
thats how a lot of suppliers get wall hammers and elegances, just take a dremmel and cut where you want it to be cut off. just avoid the mouths and put in a low flow area for a few days after fragging. ive seen hammers, scolys, plates and more cut this way
Before you do any cutting, take a rubber band and put it around the wall hammer in the same direction you plan to frag it. Leave the rubber band in place for a couple of weeks. The polyps will recede on that part of the hammer. After all the polyps start extending to their former 'glory' you can take the hammer out of the tank, remove the rubber band and run the wall through a band saw (like the Inland Band Saw) or a Dremel.
They are absolutely fraggable. They just need to be done properly.
I guess everyones right, it is doable. I was speaking from my own experience. I killed mine, it was probably an infection from the cut. Anyway its still risky.
Found some threads on this topic. They mentioned about rubberband technique and dipping after its fragged.