Yes, we are all sure. This has been discussed at great length. It's more about if you cancel the effects of a gate opening than the gate actually opening at a location, then you add a DOR token. There are 3 things that can happen when a gate opens depending on the situation, or the status of the location where the gate is being opened: 1) gate opens, 2) monster surge, 3) nothing. The DOR token is only added when that 3rd result of "nothing" is seen, as that means the mythos forces have been prevented.
We are all already well aware of how option 1 works in relation to DOR tokens: If a mythos card tells you that a gate opens at location X, and there's nothing else at location X, then you put a gate token at location X. Nothing was prevented, do not add a DOR token.
If a mythos card tells you that a gate opens at location X, but there's already a gate at location X, then a monster surge occurs. A gate might not actually be opening at that location, since there is already a gate open there, but the effects of that gate opening are not being prevented at all. "The dimensional forces are assaulting Arkham" (AH rulebook, p. 9) one way or another, be it by opening a gate or by flooding Arkham with monsters. If those dimensional forces are stopped then you add a DOR token.
There aren't a whole lot of ways that these dimensional forces can be stopped, but they do exist, and some are a little intricate, such as indicated by the OP. The main way, of course, is by Elder Sign. The only other ways I can think of are caused by Kate Winthrop's special ability.
- If a gate would open at location X, but Kate is at location X, then it is prevented; add a DOR.
- If Kate is at a location with an Elder Sign where a gate burst would happen, it is prevented; add a DOR.
- If Kate is at a location with an open gate when a monster surge occurs at that gate (note: she would have to have an explored token for this to work), the monster surge is prevented; add a DOR.
Edited by Musha Shukou, 23 December 2013 - 06:59 PM.