Special:AllMessages lists on the wikimedia wikis (tested on enwiki and dewiki)
in the first two rows[1] of every page in the list the messages "universalLanguageSelector" and "wikiLove.js".

Though the messages disappear from there when alphabetically behind their normal position.

This could also be an issue caused by the associated extensions.

[1] except for first page where below 1movedto2 and 1movedto2_redir

Version: 1.23.0
Severity: minor
URL: https://en.wikipedia.org/w/index.php?title=Special:AllMessages