We are aware of issues with non-breaking spaces and ending punctuation (particularly in French, German, and Spanish texts), but currently, Atticus is set to English language hyphenation rules. You can turn off hyphenations within your theme, in the Formatting Tab, under Advanced Options at the bottom of the page.
Atticus does sometimes split words without hyphens, regardless of the native language of the text. You can fix this by turning off “Hyphenations” within your theme in Formatting. Then you can manually hyphenate your words when typing them into Atticus.
That being said, while Atticus follows English rules for print books, it will export EPUBs with metadata of the language, which the epub reader can then apply to the user. Within your eReader, you will be able to change the language, and this will change the hyphenations within your manuscript.