[meta: I think the nesting is some sort of delay system to prevent a rapid back-and-fore argument. If you click "link" however it appears you can bypass the lack of a reply option.]
Clicking link is immediate, and the delay for an active "reply" link can be minutes. The longest I've seen (and recall the time on) was at least 5 minutes, possibly pushing 10. In an active conversation that's a long time.
