Communications compliance policies scan user messages to detect violations of company or regulatory rules. A change introduces support for hybrid users whose mailboxes are on Exchange on-premises servers. The change might not pick up many new violations, but it does increase the coverage and stops some violations sneaking through, which is always a good thing.
Office 365 content searches now support a hard-delete (permanent deletion) option for the purge action, but only for mailbox items. You can purge up to 10 items at a go. If you have more to purge, you just have to keep on purging until everything is gone. Or use the Search-Mailbox cmdlet, which keeps on proving its usefulness to administrators who need to remove lots of mailbox items quickly.