Great topic Maieshe!
Making a thread that gets a lot of traction really is tricky. I can't say that I know what makes up the magic sauce but I know what I like seeing in threads.
How does the saying go? "A picture is worth a thousand words." Having photos that relate to the discussion seems to inspire conversation. Extra points if the photos are originals and not pulled from the web.
I like threads that ask questions. Those threads can get a lot of unexpected answers which really adds depth to a subject. I have also noticed that the way a question is asked can be a boon. I personally have to keep in mind of not asking too narrowly tailored of a question because that sometimes stifles conversation.
Sometimes I am not well versed in subjects that are being discussed and I appreciate the folks who provide information to get onlookers up to speed with the discussions. Things like dynamic accumulators or humanure were foreign to me at first but Permies threads really helped fill the knowledge gaps.
Example Threads
Cooking with Dry Beans and Peas
Simple Trellis for Green Beans
The Great Big Thead of Sunchokes