It shouldn't be bannable to leave the server during combat, there's a combat tag/timer thing and your ship stays piloted so if you leave it shouldn't be a big deal. As of now if a ship is tagged by the ship that has been in the region or fires at a ship that has been tagged that becomes tagged itself it shouldn't be bannable under exploiting as it is nigh impossible to exploit, or if you exploit it by not firing back then you are of no strategic value anyway.

For example, say TheCrazyIrishGuy is firing at Akopevski, and Akopevski leaves the server, It doesn't matter that Ako left as they are both regions tagged (as Ako was firing back while running at Irish who is region tagged), when ako leaves and eventually sinks Irish will still get points. If Ako did not fire back, then he is of no strategic value and banning him is crazy.

Another thing is Connection Reset needs to be taken into account, a friend of mine got the connection reset and it appears the staff just went by visual evidence instead of checking logs. While this can be lengthy it does tend to happen during movecraft duels so it should be checked. Moreover, if the suggestion as I said gets implemented/acknowledged it won't be necessary anyway.

The only other way to exploit is if you did this to escape prep time timer, but I will make another suggestion about that.