The setting should be OFF.
ON = Use text of the currently logged on user.
OFF = Use Work Item language.
In SWI1 you can see the work item language (or SE16 > SWWWIHEAD). If the WI language is Other (OT) then logging on in OT will be a problem because both settings will tell it to use language OT.
The best option is of course to just create the text in language OT.