I sent a few questions to FFG and just got reply from Nate. Thank you Nate! Anyway, those were 3 topics that were not clear to me and I think that some people may find the below useful.
1. In Hills Of Emyn Muil quest, treacheries can gain extra surge effect if there are no locations in play. What if I draw a treachery like impassable chasm which has its own surge effect? Does surge stack so I have to resolve 2x surge and draw 2 more cards from encounter deck? I suspect that this may be a case because as per FAQ, some effects like Caught in the web are stackable (and this situation looks similar to me). Can you please confirm?
Response (quote)
Yes,
If a card has multiple instances of the surge keyword, each instance should be resolved.
2. The impassable bog reads: when revelead, add 1 token to gollum for every location in the staging area. When this text is triggered, is the just-revealed Bog considered in the staging area? In other words, does the Bog count itself as a location in the staging area?
Response (quote)
Encounter cards are revealed from the encounter deck, their "When Revealed" effects are resolved, and the card is then placed in the staging area. So the Bog has not yet entered the staging area when its effects resolve.
3. Is active location considered in the staging area?
Response (quote)
An active location is not considered in the staging area.
Edit: I asked question number 3 because in Khazad Dum there are some location that grant +1 attack to all enemies when the location is in the staging area. I was not sure if this effect still works after we travel to such location.