I think you have to look at the mechanics of the game, what they achieve and what their limitations are to understand a little of the intention of the GM / server owner and if these mechanics are being circumnavigated (aka cheated).
Take, for example, a tele ring. A tele ring allows you to transport to anywhere ON THAT MAP (where teleporting is allowed). A tele ring does not allow you to tele between maps, i.e. deeper into the levels of a cave. It is clear to me that the intent of the GM is to allow an individual to tele within a defined single level / area of a map only.
If GM was happy for a tele ring to take you anywhere in game, I am sure he would allow that.
So, why allow a recall set, where an individual can recall a group (or an individual) to anywhere in the game (where recalling is permitted)?
Personally, I think the spirt of this was to allow a shortcut for defined reasons, to either regroup in the event of a wipe, add a late starter, or grab supplies. I don't think a recall set was ever intended to be used across multiple, stationary characters to recall an individual (or group).
Why do I say this? Because of the limitations of a tele ring...
I suppose what I think matters for nowt. GM is clearly aware but hasn't made changes so he must be content. (Quite why he is content for individuals not in the guild of a castle owner to be able to enter that castle I am not sure).
Again personally, I think that obsessive individuals gaining such an advantage that they become untouchable will be the death of the server unless something changes.
However, I also have faith that the GM is a clever chap. For example, the introduction of a new top tier of kit may well make the advantages that some have gained a mute point. We will see.
It is hoped that as we now seem better able to conduct our discussions as adults, less time will be spent on moderation and more time on game design.
