On Archived pages we use magic words like __NOEDITSECTION__ to prevent unwanted editing, however an "[reply]" still appeares in those archives.
Maybe this "[reply]" should be turned of with this or a new magic word.
Topic on Talk:Talk pages project/Replying/Flow
Good point!
We can't re-use the same magic word, as there are pages that allow replying but not adding new sections, but a new magic word has been proposed in T249293.