When MediaWiki:pipe-separator contains ​ (zero-width space: code 8203) , Special:Contributions escapes and shows the code itself instead of the space.
An example is http://translatewiki.net/wiki/Special:Contributions/Whym&uselang=ja where MediaWiki:Pipe-separator is "​|​". (although this wiki is 1.20alpha, I confirmed in the Wikimedia deployment wiki as well)
Possibly other codes are affected by the same problem.
Version: 1.18.x
Severity: normal