What Blizzard staff wrote in the forum is confirmed. The language problem and the duplicated creatures are reported: Blizzard posted about the settings and sent a server message, but the problems themselves are described by players. The point about quest gold at level 60 is a rumor.
Boats, zeppelins and portals
On the first night Aggrend wrote that boats and zeppelins were "becoming lost in the maelstrom for extended periods of time". As a stopgap Blizzard spawned portals "near most transport docks or inside of the zeppelin towers", with a proper fix the next morning, after which the portals were removed. In an interview on 6 November Blizzard's designers said the transports themselves were fine. The trouble came from another service they share processor time with.
Layers that felt empty
In the same hours Aggrend said Blizzard was aware of "some issues with certain areas not feeling as populated as they should" and would tweak numbers the next day. In the interview with Kris Zierhut the reason is spelled out: Blizzard had been "a little too aggressive" about avoiding overcrowding and spread players too thin. It then raised the number of players per copy of a zone. A second forum post explains how to join your group's layer: after inviting, a blue message appears at the lower right, and its pop-up has a "Refresh Now" button.
Invited friends, language, known issues
Players who started with an Invite-A-Friend code were "unexpectedly restricted from using certain chat channels, leveling past 10, participating in guilds, forming parties, or trading items". A hotfix went out early on 5 November; logging out and back in clears it. In the EU forum Kaivax asked everyone to check the language settings in-game. Many replies describe the preferred online language defaulting to French or Spanish, which put English speakers in foreign-language layers, and a 24-hour cooldown on changing it. The known-issues list of 5 November adds, among others, a cauldron in Razorfen Kraul that traps players, PvP vendors that were temporarily unavailable, and the Ashenvale quest "Vorsha the Lasher", disabled over a crash and fixed a day later. On 6 November players also met cloned NPCs and monsters; a server message spoke of "a slight blip in the multiverse".
Rumor: no quest gold at 60
A streamer says a developer told him privately that quests at level 60 give no gold on purpose, to keep the economy in check. Blizzard has not said so anywhere we can find.
What this changes here
Nothing on the topic pages. The rulesets page already explains the language setting; the launch bug lives here.