In general, before making a new thread, it’s better to search the forum to make sure that another thread with the same topic doesn’t already exist. The Melonland Forum doesn’t have a rule against reviving or “necroing” old threads, so it may be considered more acceptable to create a duplicate even if the original thread hasn’t had a new reply in a long time.
It’s constructive to avoid repeating what others have already said in any given thread. Try reading or at least skimming the other replies in the thread before writing your own, rather than simply replying to the initial post. This is a more participatory approach that will allow you to involve yourself in the discussion.
When quoting a long post, it’s polite to remove most of the text in the quoted post and leave only the specific passages that you are replying to. That way your fellow forum-goers won’t have to scroll through a massive duplicate. If you’re replying to the post as a whole, it may be better to just mention the user who wrote it if you want them to see your reply. You can do this by typing @ followed by the poster’s username.
On a related note to the above: quoting someone’s post usually means that they will receive a notification and spend time navigating to your post to see what you said to them. If you are merely agreeing with or echoing someone else’s sentiments, or if you don’t intend to enter a direct dialogue with the other person, it may be more considerate to avoid quoting them. You can say “I agree with what (user) said”, “building off of (user)’s points”, or something along those lines instead.