Hi Edwin. After spending quite a few days of my life on this, I finally resorted to separate content types with SEBLOD storage fields set to "none" and then using BeforStore code to deal with the mySQL updates by brute force. Storage-Format/Object-user bridge is one area that I find extremely poorly documented (or perhaps it is just me :( ).
If I remember correctly, try not to mix storage (user/article) and pay attention to the dropdown settings of the content type (blue arrow at top of content type config page) >> "User" for your user creation form and "Article" for your subsequent update form/s.
Additional user edit form/s (of the "Article" object type) linked to currently logged in user via Live plugin. Select "user" for each field and set "Property*" in the "Configure" settings to the appropriate database column for each.
On a related note, with a recent 3.11.xx update, it seems I am now not able to follow my former approach in defining database tables and mySQL database fields when adding a new SEBLOD field to my user content type. I am forced now to use SEBLOD's user table.
EDIT: Please ignore above. My error. New user field creation works as before. Apologies.