Unless it is to specifically a world event i would say the limit should be specifically 3 sinks to the same team if each time you fight them is in less than 20 minutes of your last sink to them so theres a cool down and people who are playing as they go rather than tunneling wont be punished so hard.
There is the matter of people actively hunting down people already to try to force them to leave a server that we currently have already, and being sent to another server kills all voyages you have. So arguably the work around to that could be you keep your voyages if merged away due to being sunk a third time too soon to some one.
If its a fight at a world event, it doesnt count towards that so much since as it stands world events are intended and specifically designed to bring in people for interactions, whether that be to team, betray, or just downright fight over it until its complete. Even if its frustrating, interactions are the entire intent of world events so that should be fair grounds to do what ever you want.
I would say this is a pretty fair middle ground that shouldnt punish people harshly for just sticking around on a server and eventually being sunk again, keeps true to the intent of world events, and mostly alleviates people endlessly returning in any other situation. Then if it turns out people really want it to be a thing for events as well, it could be changed later with some different balance.
