For ordinary string resources, the comment key is ignored. However, for plural resources, the comment key is considered a language code.
[example_plural]
comment = Comment
en:zero = ...
en:one = ...
en:two = ...
en:few = ...
en:many = ...
en:other = ...
As a result, a file named values-comment will be generated with the resource key example_plural and a plural value corresponding to the other quantity.