Hi deperwin,
Based on your description, did you get the horizontal line as shown in the following figure?
If yes, please try this method:
Next to the line, there should be a contextual menu.
If you click on this, you should see the following options (as shown in the following figure):
Undo Border Line (i.e. revert back to the three underscores)
Stop Automatically Creating Border Lines (i.e. change the preference setting)
Control AutoFormat Options... (this will open your AutoFormat preference pane)
To check out and modify your preferences:
From the WORD menu, select Preferences...
From Preferences, select AutoCorrect
In AutoCorrect, select the AutoFormat as You Type tab
Hover the cursor over Borders, and check the description of its function below.
Have a look around the other functions and decide which you want to use as a default.
If my understanding is incorrect, please provide screenshot about your issue to our email address:
ibsofc@microsoft.com
Please Note: Please add the URL of the case in the email subject or body.
Hope it's helpful.
Regards,
Emi Zhang
TechNet Community Su