Modern editors make this a non-issue. I use both Python and YAML fairly regularly, both have significant whitespace, and I don't have any issues with either.
Also, because YAML doesn't involve things like curly braces all over the place, it's actually notably less friction to type rapidly by hand than something like JSON. I don't think YAML is amazing or anything like that but I do find myself nowadays preferring it, for config at any rate, over JSON.
JSON definitely wins for machine readable data sent over a pipe though because the lack of significant whitespace means it'll compress better.
