I'm not totally sure on this one but I think I like what Xoria said.
It's up to players to develop tactics and counter-tactics, it's not always about fairness and theres always the ignore option if necessary.
On the other side I know such a behaviour could get upset more than one person eventually leading to this topic creation but I think it's not good to have more regulations beyond the server rules (exception made for roleplayed laws and events of course).
There are a lot of situations where moving the place of the engagement to make use of environmental advantage is the only option you have available to get yourself out of trouble against overwhelming odds.
However, personally if they didn't fall into the trick I'll probably won't be coming back, accounting it like a retreat, but that's my perception.
I suppose we could try to evaluate case by case and talk with the interested subjects rather than adding another rule.
As a last resort however I'm not against codifing it somewhere if it helps.
Lo
