When I consult my Stijlgids Financieele Dagblad [Manual of Style of the Dutch Financial Daily Paper, 1999], I read this about the rules concerning emphasis on two-letter vowels (page 64):
So the Financieele Dagblad deliberately deviates from the “Green Book”. The Green Book contains the official spelling of the Dutch Language Union. The spelling of the Green Book is only mandatory for government and educational institutions; everyone else may deviate.
My conclusion: (1) The official rules are described by Paul van der Laan. (2) There is, however, no consensus ‘on the ground’ about using one or two acutes on two-letter vowels with different letters.
Except for “ij” and “ie”, there are no two-letter vowels in Dutch that start with “i”.
I searched for Dutch words that contain “fij”, in which “ij” is not a vowel. I did not find such a word—so I believe in the Dutch letter combination “fij”, “ij” is always a vowel. (I did find “Fiji” and “Fijisch” in which “ij” is not a vowel, but these words always start with a capital.)
I searched for Dutch words that contain “fie”, in which “ie” is not a vowel. I did not find such a word—so I believe in the Dutch letter combination “fie”, “ie” is always a vowel. (I did find “fiësta”, but this word doesn’t qualify because it always contains a dieresis.)
Perhaps I missed some unusual loanwords in which “ij” or “ie” is not a vowel.
Yes, this would make sense to me.
When searching for words containing “fij” or “fie”, I consulted the dictionary for which Bram de Does’s Lexicon font has been designed. I noticed that in this dictionary, in all occurrences of “fij” and “fie”, “f” and “i” were ligated—and this didn’t look weird to me. So Artur has a point: in small Dutch text, the “fi” ligature may look OK.
I don’t like a “fi” ligature in “fijn” and “fiets”. Perhaps there are other Dutch people who don’t have the same gut feeling about this.
According to the European rules for the use of the IJ in public records, in “ij”, for indicating a stressed syllable, an acute accent is placed on the “i”, not on the “j”. So a stressed “fijn” would look like “fíjn”, and the question would be how to make f+í+j look good (or f+íj, if the ligature “íj” would exist in the font involved; or fí+j, if the ligature “fí” would exist).
To me, “fiets” with ligature, looks weird directly after “fijne” without ligature. It looks inconsistent. I would prefer this:
Perhaps it looks weird because both “ij” and “ie” represent a single vowel—and with the ligature in “fiets”, half of the vowel is connected with the “f”. In “fiets”, “i” and “e” belong together, not “f” and “i”. Compare with “mies” in the image below.
The spelling of Dutch has changed over the years. In the past the “y” has been used, where today the “ij” is being used. In Afrikaans, the “y” is still being used as in the past in Dutch (Dutch: vrijheid; Afrikaans: vryheid). See here for the old and new spelling of the name of a Dutch train station.
There is a discussion here of about 580 words whether “ij” consists of one or two letters. There is no consensus about this. So, based on one’s opinion about this, “vrijdag” can be spelled in two ways: “V – R – IJ – D – A – G” “V – R – I – J – D – A – G”. Note that young school children would spell “toen” as “t-oe-n”.
It is not so clear-cut. Some consider “ij” to be a single letter, and others consider it to be two letters. Both “oe” and “ij” represent a single vowel, and are made of two letters (like “uu”, “eu”, “ee”, “au”, “ou”, etc.). At school, most children learn the language by considering all vowels to be “one thing”, even when they consist of two letters. (Perhaps the “ij” gets a special treatment with this as in the “letterkaart.jpg” image above.) With these two-letter vowels, “ij” is an exception, because only when “ij” is capitalized at the beginning of a word, both the “i” and “j” get capitalized.
I consider both “oe” and “ij” to be two letters. Lexicographers seem to agree, and they also think the “y” is part of the Dutch alphabet. See in this Dutch-English dictionary: