Okay, there is so much wrong with that statement I just have to correct it.
PWO's original developer was Kyro, who was originally from New Zealand and later moved to Australia. Following his departure from the project, server development was taken over by Xanatus - who yes, is German, but claiming he was the original developer is a factual inaccuracy.
NPCs are written by our Scripting team (now a subdivision of the main Game Editors team); which does not include the Developers and Admins although we can add NPCs too if we like. The poor NPC dialogue comes from either lack of thought, or from the team's various members being from various different parts of the globe and therefore having different levels of English expertise. In this way, you're partially correct about the language issues, but it's not the whole explanation.
As for the Mt. Silver quest, it's not particularly the messages that are the overriding problem - although that is certainly a factor in some areas - but actually, the entire scripts themselves are buggy.