Under Preferences > Appearance > Advanced options, the preference Threshold for stub link formatting should be removed from MediaWiki core and either be placed into a MediaWiki extension or be implemented as a JavaScript script/gadget.
In the code base, this is ./includes/Preferences.php, and StubThreshold/stubThreshold in various places.
The feature contributes to parser cache fragmentation, which is bad and to be avoided. It's an old, quirky feature that would likely never be implemented in MediaWiki core if were proposed today. It's merely a(n) historical artifact that it's currently in core and it shouldn't be any longer.
Version: unspecified
Severity: enhancement