Section titles are duplicated (and no section edit links appear) on pages with quotes " in the title when DiscussionTools is enabled.
(I found it a bit difficult to notice if you don't speak the language, but compare the headings to the names in the table of contents)
All reports so far are from the Hebrew Wikipedia, but I don't think this is specific to that wiki. It looks like pages in Hebrew are affected more often than in other languages, because the quote mark is commonly used for the gershayim character.
This seems to be a bug introduced in T267404, and only affects wikis running 1.36.0-wmf.30 (not wmf.27).