ORA-32598

Today we hit (while creating a test environment) ORA-32598: user names cannot be changed in ALTER DATABASE LINK command. An element of creating a test environment is the password change for users and accompanying change in db links' passwords.
As this is the 11g version, we are able to leverage the command ALTER DATABASE LINK.
We run something like:

ALTER DATABASE LINK link1 CONNECT TO user1 identified by "user1test";

And the db engine complains about changing user name, but the name seems perfectly fine. We know that this is copied from a production environment where this link works properly. But wait...
What about the etarnal problem with double quotes and names?
This is the diagnosis and solution is clear then - the db link creator in his/her command used lower case letters and enveloped the name in double quotes. On the production it works even if the user on a remote db is named traditionally (i.e. its name is stored in upper case) as apparently the connect string on the remote side is resolved as usually i.e. in a case-insensitive way.
But on the local database the user name is in lower case so if one does not use double quotes, the engine does not find the match between user already set and the name from the command. Thus the proper command should look like the following:

ALTER DATABASE LINK link1 CONNECT TO "user1" identified by "user1test";

And now all works fine...