I'll be quick and direct. There's no sense on relogging into another account after dying on UHC being allowed. If you die you die, that's it. If it's allowed, dead people with alive teammate should also get the win if her teammate wins. It's the same logic. There's no point at all on having a second chance to play just because you have access to another to another account. It definetely should be bannable.
UHC has a feature where if you log out before death match, you are still able to join back into the game within a certain time. This is for people who get kicked while playing. Since this game is a lengthy game, if you got kicked you likely put a lot of time into that game and so they allow you to rejoin. I think what you're talking about it the fact that a player (before death match) if they die and have friends that are alive, they could ask one of their friends if they could use their account and finish out the game. It's not just that you can rejoin if you have an alt account, you have to get on an account in which was currently in the game. I can see how this could potentially be unfair but I don't think it is a huge issue. When someone logs into another persons account, they put both themselves and that person at risk for getting banned if one of the 2 gets banned later on because they shared accounts. Not only do you have to find someone in game who will give the person access to their account, they also have to both be okay with the risks. I know this does happen sometimes but because of these reasons, I wouldn't say this happens to the point where it has become an issue.
I don't play UHC but I can see where you are coming from. MC-Central could make it so that two people on the same IP cannot join the same UHC game, and this could lower the chances of this happening. However, doing so could lead to issues if two people under the same house (like siblings) are trying to play together, so it could be a controversial rule. Unfortunately for that reason, unless MC-Central somehow can provide a workaround, I don't think this rule would be implemented. Players who do use alts to essentially "have another life" do however face a serious risk of being banned. Have a nice day :)
