Thank you very much for your prompt reply and swift update.
A couple of additional suggestions, still with user's data privacy in mind, are:
To have some way to set (in the backend settings) the default setting for year / month-date display when a user registers, to not being visible. Right now when a user registers, their full birthday data will be visible, and the user doesn't really know that until they verify all the profile options available.
To have some sort of "birthday date input is optional" information displayed on the registration window, e.g. on a tooltip or something.
Thinking of further enhancement - even though I'm not looking for this for my usage - would be to have the birthday registration data be verified againt a global backend setting for "minimum age to register" - in this case the data would have to be mandatory.
Many thanks again!