The future package names of a Windows Store App is automatically generated by the MS Store, made from the Contact info Publisher display name (and the Appname as the second name), when the partner account is registered (nobody told me that before, haven't seen it in the MS documentation).
I made the mistake to set Companyname Ltd, My Name as the Contact info Publisher display name and got a bad package name of my Windows Store App.
I got CompanynameLtdMyName.appname as the package name of a Windows Store App, and all non US-ASCII letters just removed making the first package name to a blur. I actually want my company's internet domain reverse to be the package first name com.Companyname that is common use elsewhere, and the only good looking solution for non US-ASCII countries publishers. These immaterial issues are quite important in marketing. But there is no such package first name field for package names in the MS Store/Partner account settings.
And I can't set com.Companyname as the Contact info Publisher display name, because it isn't. And I have to settle with Companyname Ltd that is the legal party (this is civil law topics as well), getting CompanynameLtd.appname as the package name of a Windows Store App, that is acceptable.
So I tried to change (settings, the cogwhee) the Contact info Publisher display name to Companyname Ltd and the Appname and it takes a full verification process time to make the change. MS says the verification process can take from a few days to a couple of weeks.
Well I managed to change the Contact info Publisher display name to Companyname Ltd after a few hours. And after that I had to use the second radio box in the Store/Create Your packages "..New app.." and point to the old app, to make it accept the new Contact info Publisher display name. (It should be right for the civil law.)
But the MainPackageIdentityName did not change is still CompanynameLtdMyName.appname and I guess I must register a new app name to get any change.
A perfect world is the perfect boring state of life and I don't have the effort to investigate this more.