Hi,
Thanks for the quick response. About what you mentioned:
3. When the attacking message processes to check the defender phase, it finds an existing defender, which causes it to skip the declare defender phase.
You are right that there is already a defender for the attack, but the possibility of exhausting to perform a basic defense should still be there. You cannot change the defender (for instance, choosing another character to defend) but you can choose to exhaust your identity to perform a basic defense, of course.
Thanks in advance!