Spellcheck: Support ligatures?

Germanophone users often suggest words with ligatures (fi, fl etc.), such as Profil.

In my opinion, the most straightforward way to handle this would be to allow Profil (with ligature) if Profil (without ligature) is in the dictionary.

Ideas?

sounds like a good idea, but AFAIK ligatures should not be used when the actual letters involved are of different syllables as then it would change the pronunciation of the word. (and I don’t know how you can test for that)

Ligatures are sometimes used in real offset print ; but a good font kerns the letters the same. When typing, ‘nobody’ types a ligature…

sometimes ligatures are taken beyond what kerning can do. (and I know from personal experience that manual kerning can lead to scaling issues)
EG:
A. the dutch ‘ij’ is sometimes rendered as if it’s a dotted broken ‘U’ (for example: the “PRIJZENSLAG” circle of the eponymous game-show used this to keep an even number of letters) , or as a semi-cursive letter.
B. ‘æ’, which, when done through kerning, can have the ‘e’ encroach the ‘a’ too much (or too little) when increasing the font size. (and its capitol form ‘Æ’ can only be done through kerning when italics gives the ‘A’ a straight right leg.)

In that case, all one can do is do it per word. But that can be done using a large text collection and the words list.

If wanted, I can help.