Seems there is a small issue with the sentence break in pre formatted text mode, where words are split right in the middle. Possible a side effect of normally not having automatic line breaks being applied by the renderer, which would cause the html to overflow, which the current editor (or editable) is not able to handle yet. TheDJ (talk) 19:30, 27 June 2012 (UTC)
Topic on VisualEditor/Feedback
Thanks for the bug report; I've added it as bugzilla:38043.
Is it because of the CSS class breakword?