Hostkilling for inactivity is a pretty retarded practice and something that should only be done if there's really no other option. After all you're not only punishing the person you kill, but their entire team as well (it's not like it's their fault), and it influences and at times even decides the game. It's not like it's difficult to avoid either, just plan ahead a bit and don't have everyone who signs up start, keep two or three people back as subs and then hostsub instead of hostkill.
Someone said something about subbing not working because it's a different person or something iirc (only skimmed the last couple pages), but that's not really true. While there is some change, the interactions of the first player are still there, they don't just disappear when they sub out. It's not an optimal situation of course, but a hell of a lot better than deciding the game right there.
As for dead players subbing, it can work if they died early and didn't have interactions with anyone outside the game thread. Wouldn't recommended it over dedicated subs though.
Oh and @some other comment I vaguely remember, just because you didn't do it until now doesn't mean you have to continue not doing it, given that it improves the game as a whole.