Perhaps go to this page:
https://support.microsoft.com/en-us/help/12401/microsoft-account-get-help-by-email
and select "I need help closing my account". Then fill out the form describing what you want.
Also, if you view your profile (by clicking on you account name), there is a new tab called "Privacy". On that tab there is a button labeled "Danger Zone". Click that and you can request to "Delete your account". There is a
note stating that is has no impact on your Microsoft account. It just deletes all of your activities in all MSDN and TechNet platforms, which includes the forums.
Richard Mueller - MVP Enterprise Mobility (Identity and Access)