>Are limpet radulae more likely to cause health problems (apparently gastro-intestinal problems, from what I can gather) than other radulae?  Are ingested radulae a known cause of health problems for people who consume Littorina, for example?  Or Helix?<

The problem is that the radulae are relatively large and hard to digest.  As a result, eating lots of whole limpets produces a ball of radulae in the stomach and a tummyache.
I found a pile of chitons and radulae in the Bahamas, which suggest that the locals avoid those as well.  My guess is that anythign with a relatively large radula is better eaten without it.

    Dr. David Campbell
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That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droigate Spa