So I just assume Karo knows (s)he plays this tournament?
The line is a bit vague for me then. What if X says: who wants to play doubles (and is ranked 31)? and someone else (with for example ranking 300) says doubles with X, can that also be seen as definite confirmation?!
Karo is my fixed doubles partner, and I can ensure you that she'll play singles and doubles here with me.
She just didn't have available time yet to pass here and confirm it, but according to rules, it's not necessary to be in Entries Lists.