Well the first place I visited after Braggen started Dawnguard and became a VL was Riften. Not ever having been a vampire before and having heard Honeyside was good because of the back entrance, I decided to keep a low profile and try it out. I was not sure how the townspeople would react to a vampire. I went to the stables, and in the back door, dropped the stuff of and left through the back door. I lost two NPC's in Riften doing that, took a while for the courier to catch up to Braggen. They were the only NPC's ever lost due to vampire attacks.
Later when doing a side quest for the vampires to kill a disguised Dawnguard character in Riften again Braggen went to the stables trying to keep a low profile, and then went in the front gate. All hell broke lose, not only did he get the usual thieves running around, a dragon made an appearance as well. Braggen's entry to Riften was anything but low profile. it required a reload to ditch the dragon. If he went to the stables first, Riften got a dragon each time, if he went straight to Riften, no dragon. Braggen at that point still had problems with dragons appearing whenever he fast travelled outside of walled towns. But he did not usually get dragons in walled towns. He did it in two towns Riften and Windhelm, both times he went to the stables and went in the front gate. Now you tell me, are they two cells or one? Because it was going to the stables each time that caused the problem in the town, whether it was dragons or vampires.
I'm like 99% certain that the stables outside of Riften and the interior of Riften are two entirely separate cells (perhaps someone with a PC and a view of the CS could be kind enough to set the matter straight?). At any rate, I think we're veering well away from the point, so let's back up a bit here.
I was responding to a fellow who alleged that in his game, Riften got attacked by vampires before he'd even been there for the first time, which seems quite impossible. Combat shouldn't be able to occur within in a cell that you are not occupying let alone a cell that you've never set foot in before. It's possible for combat to occur
while you're in the cell and for you to be completely oblivious to it (e.g. out of your line sight, far away, obstructed by a building, etc.) but it shouldn't be able to happen if you aren't physically in that cell. Furthermore, you cannot receive LOI's from dead NPC's whom you've never met and befriended, and he apparently did, which makes the story even stranger.
At this point you chimed in to ask him why he didn't just fast-travel to Riften even though a player can't fast-travel to a city they've never been to yet. All this other stuff you're talking about-- fast-travel vs not fast-travel, valid or not, it really has nothing to do with his issue. Even if the stables and Riften's interior do indeed occupy the same cell (which I find unlikely), and there was in fact a battle going on in Riften in real-time while he was still outside in the stables area, this doesn't explain how he's getting LOI's from complete strangers.