By default, if you make a resource calendar in Microsoft 365 (e.g. a meeting room calendar) and add it to a meeting via a calendar invitation, the calendar is configured to process the details in the email invitation and delete the subject from the meeting invitation, add the organiser’s name to the subject and strip out comments and attachments from the email to create the calendar invite.

If you wish to preserve these details, you can configure the calendar processing via PowerShell, like so:

Set-CalendarProcessing -Identity [email protected] -AddOrganizerToSubject $false -DeleteComments $false -DeleteSubject $false -DeleteAttachments $true

The default setting for all of these parameters are True:

AddOrganizerToSubject : True
DeleteAttachments     : True
DeleteComments        : True
DeleteSubject         : True

You’ve also got other calendar processing options that you might want to tweak, e.g. AllowConflicts, MaximumConflictInstances, ConflictPercentageAllowed, BookingWindowInDays, AllowRecurringMeetings and so on.