Ugh. Here's how it works.
If you TP kill, you are probably an asshole.
TP killing is often technically just PVP, and is generally allowed for this reason alone.
However, if there is an agreement in chat to be peaceful, that agreement must be upheld and staff can enforce it (by confirming with logs).
If you try to circumvent such an agreement by TPing someone else in to do the killing, you should be punished.
TP killing is frowned-upon douchey bullshit in most cases. I will not respect you for doing it. I will not defend you if a Staff member decides to punish you for doing it in what can be clearly displayed as a douche-like manner beyond simple PVP.
tl;dr: yeah, it's technically allowed, but you shouldn't do it.
