The internal structure of the forum also matters, first impressions even more.
For example, I think having the Beginner section in this forum, with explicit A place for newbies to ask questions, is sheer genius (or good luck).
Forums where beginner and advanced questions are mixed, often frustrate a subset of the experienced members (who dislike the beginner questions), and causes friction.
As an example, I left LinuxQuestions ages ago, because the moderators there required a friendly supportive attitude even for those posting obvious homework.
At StackExchange sites, the voting mechanism brings forth most popular answers, in the hopes that they are the correct ones; and that is not always true.
Because of the gamification, at SE members are also quite unwilling to admit to making any errors, and instead either ignore, or just delete their answers (which often causes somebody else to post a similar, erroneous, answer).
Sometimes, even perfectly good intentions are misread, and that leads to negative reactions; that's what happened to legacy (and his friends' vintage computing discussion board, downthebunker).
Dave is an easy to approach person, and I think that has shaped this forum a lot, to be that way as well.