I don't know if it's just my impression or what. And I don't know if it's just a coincidence. 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.
It's just your impression.
I have the impression that the same idea expressed in an OP or on page 1 or 2 of a thread is more likely to receive merit than if expressed in a comment on page 14.
That is pretty obvious. Would you ever go in the 14th page of your google search? Same thing applies for merits in these pages.
The only thing I've noticed is that when "newbies/junior members" open a thread, in most cases the did not leave any post after they've opened it.
That depends on the sub-forum. If they created a thread in Bitcoin Discussion, they may never reply again. If they have a query in the Dev & Tech sub-forum, they'll most likely reply.
Just an assumption but I guess we're gonna be heading again with the 2017 surge of newbie accounts being created and got lot more of traffic? If it's good or worthy enough to receive a merit then why not?
It's harder in practice than in theory. Not to mention that there are many spam busters in this forum; that and the merit system discourages someone to get a lot of traffic by spamming.