It is inadvisable to do so, since there may be programs which refer to
locations within that folder-structure directly.

You can quite safely change the _description_  of the user, and this will
then show on the Start Menu instead of the name. Would this be adequate?

Or, you can copy the document-folders to a new userprofile, and accept that
the settings will need to be re-created. Even so you may run-into problems
with faulty shortcuts.

When I setup laptops, I use a generic accountname such as 'user' or 'owner'
since creating a personalised account means big headaches if the username
changes. (which might not even be an owner-change, might be marriage for
example.)