@everyone saying that nobody should care,
Yes, the whole thing is a game, and it's all for fun. Of course I agree. But it is fun for me, and I suspect for some others, because we want to win, and we want to win more than anyone else. That may not matter to everyone, but it matters to me. I am an insufferable, competition addict. Feel free to call me similar names; you're not telling me anything I don't know.
captainmeme's suggestion now that his ruling is "the right one" because of the way the rule was written in the Mafia QT is unjust and incorrect.
Consider the game of Diplomacy. There are complicated moves and difficult contingencies that result in a detailed set of official rules. There may be sets of moves that nobody anticipated occurring, that result in outcomes that nobody planned, but so long as the adjudication is governed by an official set of rules determined at the outset, it is just.
Here, it matters that my death was contrary to the official rules. It matters because, while the change in rules MAY not have affected my game play, it is important that kill adjudications are not left to GM discretion wherever possible. I don't play so that a GM can arbitrarily decide whether I win or lose. So long as I am dealt with according to the official rules, I have no complaint.
It also matters because this particular rule can have an affect on the game, however slight. If the rule is oldest vote breaks a tie (as the rules proclaimed), three of four mafia members have to be online and have to agree to change a kill vote, rather than two of four. As all players can post at night, and can have all sorts of reasons to time particular posts, it matters, however slightly, to everyone how mafia kills will be adjudicated in the likely event of a tie.
Based on this, the decision here must come down to what constitutes the official rules. If you agree with me to this point, there can be no correct answer other than the first post of the thread, which presents a public and complete set of rules to all players. If an adjudication is addressed plainly in the official rules, there is no discretion. The official rules govern.
That is how we avoid arbitrary and unjust decisions, such as captainmeme declaring my death a misadjudication on the day it happened, and then changing his mind and saying it was "the right one" more than two weeks later.
It is a kind and generous act of anyone to be a GM. Nobody expects a flawless adjudication. But I think the right thing to do here is to own up this mistake, and declare it a mistake. Trivial and meaningless...perhaps. But considering how much effort people put into the game, getting the standings right should be as much of a priority as the rest of it.