> æ (U+00E6) is not a ligature; it's a mostly obsolete character, with different semantics (or phonetics) than ae.
Reading that a letter in my alphabet is mostly obsolete feels really weird. No rebuttal, just a comment.
> It would never substitute æ for ae; that would misspell the word as much as substituting an o.
While that is correct, a lot of other systems actually do this exact substition. If your name contains æ it will be substituted with ae in passports, plane tickets and random other systems throughout your life.
My own username on this website is an example of a similar substition. The oe should be read as the single character ø.
Languages often simplify as they evolve, dropping "annoying" characters like æ. In fact, it was replaced by "e" (or ae itself) in most cases as the words got imported by other languages.
A personal hypothesis is that additional characters were much simpler in the age of handwriting, most of the history of literacy, compared to the age of print, the current age.
Using handwriting, additional characters are simple and in fact Medieval European scribes used many abbreviations, etc. When you need to set type on a printing press, or even input a character not already on your computer keyboard, the barrier is higher.
It's mostly obsolete in English, which I think is safe to say and which does not conflict with it being used. For example, I think few people know how to type it into a computer, while everyone who uses a Latin alphabet can type ae.
To be fair I think most English speakers are unfamiliar with how to type most accents. But it appears to me that æ is available as long press "accented character" just like é and ë, also used in English, so they are equally reachable on mobile phone.
Reading that a letter in my alphabet is mostly obsolete feels really weird. No rebuttal, just a comment.
> It would never substitute æ for ae; that would misspell the word as much as substituting an o.
While that is correct, a lot of other systems actually do this exact substition. If your name contains æ it will be substituted with ae in passports, plane tickets and random other systems throughout your life.
My own username on this website is an example of a similar substition. The oe should be read as the single character ø.