>Fourth - I think that the use of diachritical marks is not allowed by the ICZN. Sure, not for species names (I'm unsure about authors names).<

Because scientific names are supposed to be Latin, no diacritical marks, hyphens, apostrophes, numerals, etc. are allowed in them and names proposed with those in them must be fixed.  Thus, Fusus 4-costata is now Ecphora quadricostata, for example.  Specific rules exist for a few situations (I believe German umlauts become following e), but usually the extra characters are simply dropped.  However, the author's name is spelled however the author spells it, to the extent that the medium can handle that.  Some authors use different spellings in different languages (Linne versus Linnaeus, for example), which makes citing them more confusing.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL  35487 USA
    [log in to unmask]

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 Droitgate Spa