Wikimedia Bugzilla is closed!

I need to use 

   $a = wfMsgForContent( 'serverserver' );

with Language.php having

  serverserver => '{{MediaWiki:sysopdefinedserver}}'
  sysopdefinedserver => '{{SERVER}}'

In the program, $a becomes only {{SERVER}}. 
I expected, that it is resolved down to the current serveraddress such as
http://localhost or http://www.domain.tld . I have tried unsuccessfully to use
double {{{{ }}}} constructs.

For me it looks like a bug.

Background, why this is needed:
the purpose of the construction is to allow Sysops to define a fixed server
address via page MediaWiki:Sysopdefinedserver, for example for use in the e-mail
notification body, if this is needed.