Hello,
For example, [[MediaWiki:Aboutsite]] have the default
message "About
{{SITENAME}}". But we have overwritten it by "ウィキペディ
アについて"
(translated word from "about Wikipedia").
Performance-wise it is even better, if all main messages which have
{{SITENAME}} get replacements with literals. Otherwise you're adding
up 5ms of page load time to each page. :)
Domas