Spelling pronunciation
Spelling pronunciation occurs in English when people display their literacy by using a pronunciation that more closely reflects the spelling, whether it is correct or not to do so. It is an ongoing phenomenon and can be put down to the increase in literacy over the last half century. Two common examples are pronouncing the l in "salmon" and the t in "often" - letters that have traditionally long been silent. Two counter-examples would be reinserting the first r in "February" and "library".
Depalatalisation
Much spelling pronunciation concerns depalatalisation, usually that of s, c or t when followed by i or u as an s sound where a sh is normal. A classic example is íssue: should it be pronounced *íssyûe International Phonetic Alphabet 'ɪsju or palatalised as *íshûe IPA 'ɪʃu? Clearly, the unpalatalised version *íssyûe reflects the spelling and is of greater antiquity, but is has long been the norm to say *íshûe. Even so, *íssyûe has never quite gone away, as it is perceived that resisting the urge to palatalise to the sh sound is somehow more correct. The same can be heard with tíssue, and of course there is no palatalisation in assûme and consûme: both always have -syûme: a -shûme pronunciation would sound comically uneducated. But foreigners should learn to palatalise words that normally have this pronunciation, if they are not to sound mannered. Nobody says *insyûrence for insûrance; indeed it most often sounds like *inshŏrance.
And sûre itself retains its palatalisation: AmE *shûre, BrE sůre certain = shŏre sea: it does not sound like seŵer. spêcies however has been showing signs of returning from *spêeshíz to *spêessíz or *spêessêez. Meanwhile, Cambôdia, ‘Cambodge’ in French, was for a time in the 1990s Kampuchêa in English: we can see that the -dia represents a palatalisation to a j sound that has been lost in English, and that the K- spelling was an attempt by some to restore it in the form of a ch.
Other words not normally palatalised are: assûme, dûe, ensûe, euthanâsia (-zìə), Galícìa, Parísìan (-zì-), presûme (-zyûme), pursûe, redûce and other words in -dûce, sûicide, sûit (cf. shoôt), synaesthêsia - though anasthaêsia might be (AmE both -nəs-), Tunísìa (BrE *Cheŵ-nízier) and Valéncia. Other normally palatalised words are: amnêsia (-zhə), apprêciâte, Âsia, assôciate, atrôcious, caucâsian and other words in -sian (-zhn), Chrístian (*Kríshchən) and other words in -tian (-shn), Indonêsia, milítia, negôtiate, Patrícia, Përsian, pléasure (-zh-), précious and other words in -cious, préssure (-sh-) and other words in -sure, sôciology, sôldier, substántial, Croâtia (Crô-, and other words in -tia), vísion and other words in -sion (-zhn), vítiate, volítion and other words in -tion (-shn).
Another spelling pronunciation is Colómbia for Colòmbia (= Colúmbia British, trademark), unnecessary, as there is no danger of confusion. In óften, normally *óffen, many people pronounce the t; a regular pronunciation of âi in agâin and agâinst can sometimes be heard instead of *agén and *agénst; toûr alternates with tŏur; BrE pŏor increasingly sounds like poôr, although dŏor remains unaffected.
Lengthening of -íz to -êez
From around the beginning of the twenty-first century, another very strong tendency, perhaps influenced by the spelling pronunciation of some foreign learners, is to lengthen the vowel sound in the ending -ies in nouns, but, interestingly, not in verbs (cárries is still *cárríz). Traditionally the -êez sound is used only for the plural of words from Greek ending in -is: crîsis, plural crîsês (*crîsêez), but it can now be heard in the plurals of nouns in -y, such as pàrties:
traditional > trendy
-íz (= ís) > -êez (= êase)
pàrtíes (*pàrtíz) > pàrtìês (*pàrtêez)
fámilíes (*fámilíz) > fámilìês (*fámilêez)
Similarly:
he’s (*híz) > hê’s (*hêez)
she’s (*shíz) > shê’s (*shêez)
I have also heard bâby’s pronounced this way: is it now spreading to the possessive as well?
This appears to be the continuation of a change, as we can hear in films from the mid-twentieth century how the -y ending too was once pronounced í.