Pressing enter after placeholder inserts new block

[frumbert]

In the demo, type in the first row. instead of pressing down-arrow to get to the next line, press enter.
On the next line you are typing in whatever the default block object is for that browser. In chrome and safari it's a p. In Firefox it's a div.

On the last entry pressing enter duplicates the item, which may or may not be intended (in my case I like it, but it's also reported as an issue).