Compact language links allow the user to search languages in any language. This is convenient since users may look for a language such as Spanish by "spanish", "español", etc.
However, this also may result on the autocompletion to show results in languages unknown to the user that may cause confusion. For example, when reading a article on English Wikipedia, I try to search for Spanish by typing "spa" and I get the suggestion of "spanyänäpuk" which I assume it refers to Spanish, but I'm hesitant to confirm such selection. In this case it may have been better to give priority to the languages more close to the user context (e.g., the language of the wiki, and common languages) instead of going alphabetically.