Uncaught IndexSizeError: Failed to execute 'extend' on 'Selection': 1 is larger than the given node's length.
the same error happens when trying to remove the heading as well.
Replace the append content button/toolbar by the AlloyEditor's add content toolbar
Styles toolbar not updated after using the remove button
Merged in master in https://github.com/ezsystems/PlatformUIBundle/commit/75c394550bec24c67bb72690e4f3b26779beaf65
Issue only reproduced on Chrome. In Firefox the issue does not seem valid as with and without the fix the issue does not happen, a <br> tag is present inside the HTML element even without the fix.
Note: the Chrome vs. Firefox thing was mentioned in the "Environment"