Moderator status is granted by the board owners (salesforce.com). You'll never be a moderator unless you become a salesforce.com employee (or you make friends with someone that could grant you that status and had a good reason to do so). Our moderators are usually internal salesforce.com Developers, from what I've observed. I've been an SC for so long, I don't even remember when I reached THAT plateau... I don't keep track that way. I think SC status is granted around 250 authored solutions, as opposed to a number of threads/responses, but I'm not actually sure; I didn't notice when I moved up to SC, and when I looked at my stats, my thread count wasn't some even number, but my authored solution count was.

I do recall that my Signature used to suggest that users should be accepting solutions to help keep the board clean (e.g. you can see at a glance if a thread is solved), but some other community members pointed out that it seemed that I was guilting members, which wasn't actually my intent, but I felt it was appropriate that I adjust my signature accordingly, because I don't want to be seen as someone that's just looking to collect stats. I like helping people, and I just wanted to make sure that others would help, too. I felt bad about it, so I came up with my completely useless signature whilst I prepare my blog. While I do wish more people would mark solutions so I can skip over threads that don't require any further assistance, I just have to place my faith that people will discover that you can accept solutions and use it meaningfully.