This issue is still not addressed as of Twenty Sixteen v1.3. I just fell victim to it, and was about to post a bug report of my own when I happened to find this one.
Here are some screenshots that I took with stock Twenty Sixteen v1.3, in case it isn’t clear to the maintainers what the problem is. In short, it’s the editor styling that’s b0rked – everything else, including the underlying HTML, is correct.
Text editor:

Visual editor, with its actual HTML (courtesy of Chrome Dev Tools):

Preview:

Are there any plans to fix it at all? Thanks much!
-
This reply was modified 9 years, 8 months ago by lexfiend.
-
This reply was modified 9 years, 8 months ago by lexfiend. Reason: Changed one screenshot and added details for clarity