This leads me to the question: do we need any other form of rewards other than merit?
No.
Merit works, it's doing it's job of preventing much spammers from ranking up
Maybe in the past, but not anymore. There are far too many shitposters ranking up lately to say that merit system works as intended.
In the neighboring forum - Altcoinstalks, the admin decides and implement. In some cases, milestones are set and when you hit it, you'll automatically be rewarded with a bad.
There's a badge for making 2 posts with 60 secs and such similar type of badges that could encourage spam.
There, you'll be rewarded with a star, when you keep creating topics/threads.
There reality here is that theymos doesn't have that time. Infact, Satoshi doesn't seek recognition, otherwise he would have been here collecting more awards, rewards and badges.
This is what an average altcointalk profile looks like to me. Who in their right mind would want to see it here?

Ah damn it you beat me to it, this was my first impression in relation to the OP.

Look the merit system is in place to reward everyone, those with over 10k merit are already known.
If we create something extra, an additional form of recognition then in time there will be a call for
another add-on.
The members with the highest ranks are not interested in any extra sort of recognition, they have already
reached the legendary position, no need for Double Legendary, Super Legendary or Ultimate Legendary.