How can I prevent CiviMail Bounce Processing from moving mail to "ignored" folder?
Bounce processing assumes that the account is dedicated to handling bounces.  You don't want to mix bounce handling with a mailbox used by users.

See all of the "CiviMail setup" chapter in the System Administrator Guide and in particular:


https://docs.civicrm.org/sysadmin/en/latest/setup/civimail/#bounce-processing
https://docs.civicrm.org/sysadmin/en/latest/setup/civimail/#verp-support
https://docs.civicrm.org/sysadmin/en/latest/setup/civimail/#special-email-address-for-incoming-email
https://docs.civicrm.org/sysadmin/en/latest/setup/civimail/#adding-an-incoming-email-account-for-processing-bounces-andor-email-to-activities
https://docs.civicrm.org/sysadmin/en/latest/setup/civimail/inbound/#bounce-handling