The only thing I glean from karma on pros is who flakes and who doesn’t. Most people write such superficial comments in karma that it is hard to tell one recommendation from the next. As far as the forums go I agree with @MCcuddles2. Hard to say what someone is really like from posts except for @sillysassy (she is exactly that in real life). There have been a couple of instances where I met someone who rubbed me wrong in the forum and they were actually the opposite in real life. However, I do have a peccadillo regarding posts from pros in the forum. I do not book with pros that love to brag on themselves and talk about all the ways they are a great pro and so on. They might be and it might just be me but it rubs me wrong. But there are so many pros that never even post that I do not see this as problematic for those that do.
As far as enthusiasts—the only way I choose is through DMs. To me, enthusiasts are a whole different dynamic, and usually much more rewarding long term. But I have been burned before by a psycho enthusiast. Another day, another story.