CSV has the same failure mode. As does HTML. (But not XML)
And fully fair that you can have similar issues in other formats. I think the complaint here was that it was a bit harder, specifically because it did not trip up any of the loading code. With a big lesson learned that configs should probably either go pascal string style, where they have an expected number of items as the first part of the data, or xml style, where they have a closing tag.
Really, it is always amusing to find how many of the annoying parts of XML turned out to be somewhat more well thought out than people want to admit.
Still, fair point. And is part of why I said it is a flaw, not the flaw. Plenty of other reasons to not like YAML, to me. :D
Still, a fair point.