The reply link does appear eventually; there's just a delay that gets longer as the nesting gets deeper. It's supposed to slow down rapid back-and-forth thread

The reply link does appear eventually; there's just a delay that gets longer as the nesting gets deeper. It's supposed to slow down rapid back-and-forth threads that are usually between just two or a few people, often are arguments, and occasionally "take over" posts by generating dozens of comments.