Applies to any use of a messages using {{SITENAME}} in the interface, but not in the content/when visiting the MediaWiki: namespaces message pages themselves. This results in weird inconsistencies, such as the site banner in some skins not being converted (CologneBlue, Example), and the tagline, despite the rest of the interface being converted around it, as well as the entirety of the content itself.

See: https://sr.wikipedia.org/w/index.php?title=Главна_страна&variant=sr-el&useskin=cologneblue (latin variant serbian):

Timeless works around this by forcibly passing the banner message (which also defaults to {{SITENAME}}) through language->convert skin-side. Similarly, srwp has separate tagline messages for each language variant, none of which use {{SITENAME}}, to ensure they display correctly was well. None of this should be necessary.