+1. If I go with the comment option, then I'll sometimes write a comment like "If you change this here, then you must change it everywhere with this tag: UNIQUE

+1. If I go with the comment option, then I'll sometimes write a comment like "If you change this here, then you must change it everywhere with this tag: UNIQUE-TAG". This way, the reader can just do a global grep to find all the places to change, and you don't have to list them in each place and keep them in sync.