There are two ways to reply to a forum posting, using the "Reply to this" button on the previous post and using the "Quick reply" form at the bottom of the thread. Each has its own benefits and drawbacks. Here are some suggested uses.

Use Quick reply at the bottom of the thread when you are replying to the last post in the thread or when you are just adding to the overall discussion, not necessarily a specific post. Your post will become the last post and be read in that order.

Use Reply to this only when you want to directly quote something that someone else said that is not the last post in the thread. Make sure to only quote the parts you want and not the entire thing. Your post will also become the last post in the thread, but will have the quoted section.