Live preview feature fails to parse the system message MediaWiki:PreviewNote on frwiki. jqueryMsg.wikiTextToAst fails when it encounters the character {. It seems that wikitable syntax is not supported. It seems linked to the commit pushed to resolve the ticket T190120.
mediawiki.jqueryMsg: previewnote: Parse error at position 26 in input: <div id="previewnote-fr"> {|