[Ndymium]

En and em dashes are easily accessible on both my laptop's and phone's keyboard layouts and I like using them, just like putting the ö in coöperate. It's sad if this now makes me look like a robot and I have to use the wrong dashes to be more "human".

[unwind]

TIL that some people spell cooperate with an "ö".

As a Swedish native it really breaks my reading of an English word, but apparently it's supposed to indicate that you should pronounce each "o" separately. Language is fun.

[cap11235]

As a native English speaker, it also breaks my reading of "cooperate". Never seen it before. I think parent is just annoyingly eccentric for the sake of it.

[Freak_NL]

Using umlauts to signal that a vowel is pronounced separately is common in a number of languages (like Dutch).

[jnwatson]

Em dashes are widely used. The diaeresis is only used in The New Yorker and those that copied their style.