Is it not possible to have any pending teleport requests cancelled when entering /warp pvpmine? Lately a few people have been asking for island help, then when you teleport they quickly warp pvpmine, jump into the combat area, and kill you for whatever you have on your person.
Next time this happens, tell a staff member and the situation will be dealt with. As for the teleport request, dont accept teleports of random people, helping is good but if you dont trust it warp to pvpmine yourself and accept the tp there, that way you can see if the person is there and cancel it (by walking) if he is.
I feel that's too much of a burden on any good actors though. Due to lag and human reaction times, it might also not be a very reliable way of preventing said tpkilling So far the only tools we have to protect ourselves are with video evidence (I am VERY outdated on this subject matter) and even then, Potato PCs might not be able to do it at all, or atleast while giving us a playable expereince