Skype security flaw or dubious architectural decision?(answers.microsoft.com)

https://answers.microsoft.com/en-us/skype/forum/skype_accountms-skype_privacyms/security-flaw-participants-that-left-chats-can-see/585c310c-cde9-48f3-9b5e-a65d50d80f09?tm=1515165025508