For some reason, copying text between documents sometimes copies attributes for text and paragraphs across as well. So when I copied a block of raw text from one document it also seemed to enable hyphenated word-wrap (for that paragraph at least).
Anyway - to enable or disable this:
- In Writer's top menu, select Format -> Paragraph.
- In the Paragraph window, click the Text Flow tab. The first heading is Hyphenation; deselect the box to disable hyphenated word-wrap, or click to enable it.
If you enable it, the options (e.g., Characters at line end/begin) seem pretty self-explanatory.