Your concerns & questions are certainly valid ones.  With regard to the risk factors, there have been a multitude of posts on the subject & a great deal of very helpful information.  

There are certainly some conflicting opinions about what constitutes an acceptable level of risk for any particular activity, but that's for each of us to decide for ourselves.  Nothing in this arena can be 100% risk-free, but that can be said about everything in life.

I've had providers mention their test results just in ordinary conversation, but it's never really been talked about as an issue nor has the question been asked.  While there've been an isolated thread or two regarding someone's test results, it's not a standard practice.  Frankly, I don't know that it should be.  How could honesty be guaranteed without revealing confidential information?  And even then liars always seem to find a way if they search hard enough.  Besides for certain types of STDs, HIV as an example, it may take some time after the individual becomes infected before it would be revealed by testing.  That's why I personally feel it's important for everyone involved in this hobby to be tested regularly...& yes, that includes the guys.

As to posting that you contracted an STD from someone....that's a real Pandora's box IMHO.  Forgetting the legal issues (if there are any) there's already enough crap going around from time to time that, whether true or not, is unsubstantiated.  What better way for some unscrupulous individual with an agenda to damage somone else than by posting something like this?  I hope I never see anything like that on TER.