If a topic gets long, naturally people may not read every post. Someone may comment without realizing that their opinion has already been voiced and replied to.
Rather than replying to them with a quote from above and adding another post to the topic as a whole, perhaps there could be a feature where users can refer each other to previously posed comments within a topic. The references could appear in a similar fashion as quotes do already except that these would not be appended to the entire topic, but just appended to the comment of the user who must be referred to a previous post.
Might make for a much more streamlined experience.
I find that often, I want to respond to someone’s comments, but my response would add nothing new to the conversation. So I do nothing because I don’t want to overcrowd a topic.