Your idea is good because it does not require intervention by the admin, but since there will be those who will not read the rules and will make this fatal mistake (maybe accidentally) and thus be disqualified, it would certainly be better to merits be completely disabled in that thread. Either way, some of it would be desirable to apply.
I suggested penalties either in this thread or the one in Meta regarding the merits. Theymos doesn't have to intervene at all in that case. For each merit that a candidate awards in the thread, he will have one vote removed from his total count. So if you get 20 votes for a certain category, but your rewarded people with 10 merits altogether, 10 of your votes would be disqualified. Ultimately, your final count is 10 votes.
Yes, it's a very reasonable idea. There's no doubt that some of the voting members are purely driven to nominate users giving out Merit if you nominate them. It's obvious and somehow an act of "buying" nominations.
I sent two or three merits in the voting thread, I did it somehow automatically when I received the mentioned notification. it was only later that I considered that this could be misinterpreted as a vote-buying. My mistake.
I never intended to force myself to receive any reward from there, I would withdraw my participation in the nominations, so whoever does the final count can leave me out.
Yes, if you did it only a few times, it should be no problem.
It's more problematic that some people have merited every single time, when someone nominated them. And by doing so, it was incentivizing easy Merit grabs. I would also suspect, that probably a whole bunch of alts voted, if you check some of them, they barely write in other sections than Altcoins / Bitcoin discussion / Trading (traditional signature spam sections) and suddenly posting in that topic about Bitcointalk awards.