The pages for the N'Ko (nqo) incubator are shown in LTR direction, even though this is an RTL language. For the Algerian Arabic language (arq) they are correctly shown as RTL.
The same problem happens for translatewiki.net: while translating, the translation editing box is LTR.
This probably happens because there is a MessageArq.php file, but no MessageNqo.php file, and the language is not defined as RTL in any place that is accessible to the WikimediaIncubator class which customize the page language, or to OutputPage or SkinTemplate, which actually set the page direction.
The MessageNqo.php file will certainly be created when this language reaches the threshold for importing translations from translatewiki.net to MediaWiki core repo, and then it will not be a problem for this language any longer. However, this will be a problem for other RTL language who will want to start an incubator, so maybe it would be possible to create a way for the Incubator extension to know the direction for languages that are not in Names.php and core languages yet.
Another possible solution would also be to have wgExtraLanguageDirections in addition to wgExtraLanguageNames.