Skype needs a huge improvements in privacy and integrety protection settings
GDPR stipulates that no Personal User data should be collected, leaked, displayed, transferred, processed and so on.
Any processing, collection, displaying of personal user data is illegal if there's an alternative way, or a less intrusive way to solve the task for whatever the reason was for collecting or processing said personal information.
GDPR also stipulates that unless Microsoft has a significant business based reason for collecting and processing any personal data, the benefits for the user must outweigh the privacy and integrity violation of said personal data.
Everything in Skype is Personal Data according to the definition in GDPR.
Microsoft need to introduce opt-in for basically everything displayed in a remote client, from user name, county, email, location, onlinestatus, time since last active and so on.
Anything not needed for the operation of sending a message needs to be opt-in.
You can have a user in skype, displayed as AnonymousUser#1, with no other info available, and still have all the functionality of sending messages and making calls.
And since any personal data being collected and processed by skype obviously is done with the justification that it is necessary to provide a text chat, voice and video communication service, then GDPR stipulates that only the minimum amount of personal data can be collected and processed.