Hard lines appear between each line of text on some pages, not others. How do I prevent unwanted lines from appearing?
You may have inadvetently applied attributes to the text by some action. Assuming the lines are either produced as upper borders of the paragraphs or of the characters:
Select all the text in your document showing the unwanted lines, and press Ctrl+M (Clear hard formatting). If this doesn’t help, report here again.
Please note: If there are applied additional direct attributes, they will also be deleted.
As with any unwanted effect: Press Ctrl+Z to get back to the previous state.
What are hard lines?
"It could also be the font effect “Overlining.”
This was what I had in mind when talking of character attributes. The attribute is also offered by the editor for paragraph styles, because a paragraph style comes with default attributes on the character level (including font, font size, …). All these default attributes are overlaid if a character style or direct character attributes are applied to a part of the paragraph’s text.