Thread:Project:Support desk/Suppressing replacement of line breaks with spaces

When editing plain text in a text editor, then copying it and pasting it into the MediaWiki edit field, all line breaks are replaced with spaces (immediately upon pasting, not upon submitting the edit). How can this be prevented (i.e. so that it functions like the edit box for this wiki)? This behaviour does not depend on whether the text editor's word wrap setting is enabled or disabled.

MediaWiki 1.16.2/PHP 5.3.8 (apache2handler)/MySQL 5.0.77-log. Wiki is restricted; can't provide access.

See also.