The moderator of that post appears to be making a judgement call as opposed to stating actual policy.
Multiboxing is very simmilar to botting and 3rd party programming so according to Anet’s policy it is strictly forbidden
From
Is ISBoxer allowed?:
But I've heard that "Third Party Software is not allowed!"
First of all, that is wrong regardless of the game being discussed. It's impossible to play any PC game without using any "third party software". The game itself relies on third party software, such as Windows and DirectX. It is a common misunderstanding of the terms set forth in a game's EULA/ToS/ToU. "Third Party" does not imply that you are doing anything wrong. All it means is that the software does not come from the First or Second parties, which are the game publisher (e.g. Blizzard) and you. In our case, I am the Third Party. Both Blizzard and Sony Online Entertainment have either explicitly or implicitly allowed software that I provide: WinEQ 2 and EQPlayNice have been staples of EverQuest multiboxing for several years, and Woody from GUComics got an answer long ago, directly from John Smedley, saying that they would not ban for using EQPlayNice; A few years ago, Blizzard inadvertently banned WinEQ 2 users, but then reverted those bans and gave the players 2 days on their subscription time to make up for the mistake (similar to what happened when Blizzard inadvertently banned Linux players). Clearly, "Third Party Software" is allowed, as long as it abides by the rules set forth in the EULA/ToS/ToU.
There are other types of software that are also allowed. Some other common examples include video recording software (e.g. FRAPS), voice chat software (e.g. Ventrilo), even in-game instant messaging software (e.g. X-Fire, though note that if you try to use X-Fire in-game features with ISBoxer you may experience a performance hit).
To drive that point home... here is a quote directly from the
Guild Wars 2 User Agreement (terms of service)
You further acknowledge that use of the Software may require additional licenses, such as a license to any applicable operating system or other third-party software, and that You are responsible for obtaining and agreeing to any applicable third-party license before You enter into this agreement.
Just because something is third-party, does not make it inherently bad. And clearly this moderator does not have this understanding. It's not uncommon to see posts like this from GMs who aren't up to speed on the particular issue, and likewise there are sometimes bans that get reversed. (Reversals have been posted from Aion, RIFT and Vanguard in the last year)
I personally met Mike O'Brien and Pat Wyatt (who is not there anymore, obviously) around the time Aion was coming out (NCWest was dealing with both GW and Aion), and we had lunch along with a couple of developers, and while I was there for other reasons, we talked a little bit about multiboxing. They didn't seem to see a problem with what we are doing, and besides the game does a fairly good job of preventing multiboxing as a matter of game design as opposed to a matter of rule enforcement.
Anyway... I obviously don't have the final answer from ArenaNet but it should be fairly obvious to tell the difference between bots and multiboxers in GW2...
With that said, thank you for pointing out that post.