Content change flag in editor is not corect, so this condition doesn't work in decorators/effects.js:
if (original == newContent)
as some newline is prepanded to newContent always.
Tested when wiki editor is set to open by default in global settings this may be difference as couldn't reproduce on your demo site.
But changing the above to:
if (original == newContent.trim())
works fixes the bug.
Don't think surrounding spaces will ever matter in this case so trimming them.