What is clear is that if you open threads (if they don't suck) it's easier to get merits. I don't know if they know it and that's why.
Not true at all. If you are generating quality post, you will get merit. No matter it’s a reply or a thread itself. Without quality, no matter what you create, you are unlikely to get merit.
Regarding creating thread, I see no problem with that if the topic is something to discuss about, if the topic isn’t discussed hundreds of times. Then there's nothing wrong to create a thread.