I have found in our specs at two places information about this:
File Format 1.0.2
Line type 2 can also be used to represent fine detail in patterns (cf some torso patterns) and when used in this manner any colour may be used for the line. In either case it should be remembered that not all renderers display line types 2 and 5.
Official Library Specification for Sticker Parts
Since edges are forbidden in sticker parts, colour 24 is not allowed.
So I understand both documents in the following way:
Usage of lines in another matter than egdes is not forbitten, only in sticker parts if they are submitted to the PT.
File Format 1.0.2
Line type 2 can also be used to represent fine detail in patterns (cf some torso patterns) and when used in this manner any colour may be used for the line. In either case it should be remembered that not all renderers display line types 2 and 5.
Official Library Specification for Sticker Parts
Since edges are forbidden in sticker parts, colour 24 is not allowed.
So I understand both documents in the following way:
Usage of lines in another matter than egdes is not forbitten, only in sticker parts if they are submitted to the PT.