I don't know the best way to handle this, but I don't think an intricate, overly complicated ranking / voting system is the answer. I hate reputation systems as they almost always turn into an elitist epeen contest, and frankly, if that's what you're into, you're in the wrong forum.

I'd be content hiding join dates / post counts from the general population. I don't have a high post count compared to others, but I consider myself pretty knowledgeable about content we discuss here. Post counts and Join Dates aren't always everything. Your credibility is about the only thing you have here, some have it, some don't. You're post history and your attitude goes a long, long way is the major factor in how people treat you. There's plenty of examples of this in locked threads.

Users should be allowed to make up their own mind about someone, but they should also be protected from the dangers that they may not be immediately aware of, and should be warned before taking any advice from someone who shouldn't be giving advice.

A lot of advice I see getting thrown around goes along with: Those who can, do. Those can't, Teach. It's kinda scary, but I usually let it go because people are trying to contribute and people should be encouraged to share info and experiment.