I get the expected behavior in Emacs 27.0.90
* x
asd fnjkasn dkfjan ksdjfn kajsdfn
* kill this whole header line and insert before caret
^ajsdf kasdn kfjasnd jkfan ksdfn
what i expect is that it is inserted above caret
what occurs is it gets inserted below
* z
Le 18/07/2020 à 01:18,
in recent maint in emacs 25.
* x
asd fnjkasn dkfjan ksdjfn kajsdfn
^ajsdf kasdn kfjasnd jkfan ksdfn
* kill this whole header line and insert before caret
what i expect is that it is inserted above caret
what occurs is it gets inserted below
* z
this is surprising because i expected pl