ospalh quoted Shady Characters by Keith Houston
The Chicago Manual of Style( …) suggests that hyphenating more than three lines in a row is undesirable (…), yet Gunenberg managed ladders of eight consecutive hyphens.
— Shady Characters by Keith Houston (Page 130 - 131)
Well, CMS is an Usonian style book. Let’s look up rules for German: »Mehrere Trennungen hintereinander sind natürlich nicht erwünscht, aber zu dulden« »Several hyphenations in a row are obviously not desirable, but to be tolerated.« (Detailtypographie, Forssman & De Jong, 8th ed., p. 130)