I suggest that anyone who has enough free time to be interested in the
Mollusc/mollusk question nip out and buy themselves a copy of Baugh and
Cable's 'A history of the English Language'. This has recently been revised
and reissued as a paperback, and on top of its enormous value to anyone
interested in English is also a superb read. In there you will find all the
reasons why these semantic squabbles are a waste of time - and this from
me, the most pedantic nit-picker of all - and eye-openers such as :
- in the twelfth and thirteenth centuries, most people who wrote anything
in England used French, as did most educated people in conversation
- the American forms of words such as 'color' and 'valor' are older (in
usage) than the fake 'Frenchified' 'colour' and 'valour', which date from
the Regency;
- hundreds of words in English are objective synonyms of others, having
come into English independently via Danish, Norse, French and German.

All one can say is that one can't say much about what is and isn't correct
in English. Could be worse - could be Japanese.