The inconvenience isn't important when it's an outlier event.

Does everyone bungle their Skype account profile 3 times a day or did it happen to one person out of millions and only one time in that person's life?

For outlier cases, any form of redress at all is ok. All that really matters is that there IS a procedure at all and it is doable (doesn't cost $1000 or require something impossible). Unlike say getting your google/gmail account fixed when there is no such thing as a google customer support # you can call to fix things that the automated processes got wrong.

The only problem I see is the discrepency between creating and updating.

If there is a valid reason to require proof of age to update an account from child to adult, then by rights exactly that same proof should be required to create the account in the first place.

then the convenience matters, and there should be some more practical way to supply something which is legally accepted as good enough, and that should be the same for both creation and update.

I don't think we really have that "something", especially not globally and absolutely positively not anonymously. By now, in most countries there is probably some form of standard ID that most people in the country either have or can get. But they are different for every country and definitely creates a first world discrimination filter.

Thinking about that, it seems like the whole idea is misguided and imvalid, unworkable. How would one do it? Even in a 1st world country and me having both a SSN and a drivers ID and or government ID, it still leaves the problem of anonymity and multiple/temp accounts etc, and still leaves the problem that I entered the wrong number which means probably someone ele's number, which means someone else could enter mine...so there needs to be a mechanism to prove that I own the number I entered, which there is no such mechanism. Maybe if ID#'s were really key pairs and you never simply entered a number but instead signed something or proved that you could decrypt something signed, but that is a high tech fantasy world we aren't quite in yet.

Kids should be protected from those who would exploit them, but requiring proof of age to use on-line services isn't a functioning way to do it.

Fair enough, but I’m not sure Microsoft could be described as a ‘random company’