Black lines behind text box

I'd start with Rule Below Paragraph:

1. Select the text with the Type tool
2. Open the Control Panel menu (the button to the right of the lightening bolt):
   
3. Choose Paragraph Rules:
   
4. Check Rule Below (and because the rules can be offset to move up and down, Rule Above, as well). Make sure both are unchecked.
   
5. If this works, and if you are using styles, right click the style name > Redefine Style to update the style definition. If not, come back and let us know.

It doesn't look like A strikethrough.  Check Rules, Paragraph Style options>Paragraph RUles.  Also on mac cmd+option+J will bring up the Rule options. not sure on Windows.

If you don't see none of this in Word itself, most likely your default ParaStyle in ID (possibly [Basic Paragraph]?) is modified.

Carefully check all options: Paragraph Rules, Underline, Strikethrough, Shading... Reset them to None.

Or maybe some Character Style is On by default and so applies to every new text. When nothing selected ChStyles normally should be set to [None], too.