Outlook treats a forwarded invite as an invite. Notes treats a forwarded invite as an email and you have to notify the original sender to add because of the fear that there will be not enough seats in the meeting room.
This is 2018. Please change this anachronistic Notes behaviour.
So many comments and ideas already relate to the archaic look and feel of notes itself. I am a very happy user of IMSMO and have migrated all my mail over to Outlook.