Thanks for letting me know about the typo. The dot space is used to mark arguments since some arguments span multiple lines but are connected. For example, in

Thanks for letting me know about the typo. The dot space is used to mark arguments since some arguments span multiple lines but are connected. For example, in Theorem: . for: x where: y then: z . 'some statement' the 'for:where:then' group together is one argument, while the 'some statement' item is the second argument. The dot is needed to distinguish from Theorem: for: x where: y then: z 'some statement' where it is hard to tell where one argument stops and another starts.