While working on a demo site (madcityzen) I was unable to hide article titles.

1. Added a new article on the page.

2. Entered new content in Description area.

3. Under Display tab, set Display the title? field to No.

4. Saved. Upon returning to page the article title was being displayed.

5. Clicked the article's edit button, noted that the field had reverted to Yes. Set it to No again, saved. Again, the title displayed. Repeated, same results.

I also went to a new demo instance, added a new page layout to the site and added an article to it to test this with the same results.