Oh interesting, that's actually some other mod, presumably "Extended Descriptions" (?), that is adding the mod setting default value to each mod setting. Because it cannot detect whether a mod setting has been given a description, it has to assume that it has, and concatenate it with its own info. In this case my mod settings don't have descriptions, so it gives the error seen.
I don't think my settings require descriptions, so I don't want to add them. You should report this to the mod that actually adds the default setting descriptions - they should remove that feature anyway because hovering over the 'reset' button shows it since 1.1.61.
