Comment from Arno Wouters

For what it is worth .....

I made a document in TextEdit with four lines:

Conrad likes coffee.
Alice likes ale.
Bob likes beer.
Donald likes donkeys.

I could turn this into:

Alice likes ale
Bob likes beer
Conrad likes coffee
Donald likes donkeys

in the following way:

- place the cursor at the beginning of the second line (just before 'Alice')
- press ctrl-K 4 times,
- place the cursor just before 'Conrad' (for example by pressing the up arrow key)
- hit ctrl-Y

So, indeed, performing a second kill *immediately* (without doing anything else) after the first one appends that kill to the kill ring.