I'm used to have all non printable characters visibles, but since 3.4.3 printing the document has the effect of resetting all this options.
- open a doc with writer
- options - writer - formatting, and set all "non printable characters" checkboxes
- save options
- print the document
- options - writer - formatting: you'll have all "non printable characters" checkboxes unchecked
*** This bug has been marked as a duplicate of bug 40482 ***