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's just my impression though. I don't know if some statistical savant like DdmrDdmr will have statistics on this.
I think you have the right impression, though I'd be curious to know for sure with statistics. What I do know is that I've noticed the same thing--and it's most likely because if you have a 14-page thread, members are much less likely to actually read all the way through it (unless it's a very juicy drama thread of the type we'd get in Meta when Lauda and Vod were around).
And OP, no I haven't noticed noobs or Jr. Members starting up a lot of threads as of late, but I've got a lot of sections on ignore and thus could be missing them if that's the case. But I do think new members think (rightly or wrongly) that if they create threads they're more likely to earn merits for doing so. Sometimes they do, but older members--usually ones with sMerits to give out--tend to be very skeptical about threads like that, since so many Newbie/Jr. Members have created threads in Meta about topics like merits, trust, or whatever, and they usually come of as blatant merit-seeking posts.