Well, yeah. Some of that has to be taken on a case by case basis, but in the situations I mention, I think it's best to keep it private most of the time. In a case someone kills you're character and you see how they abused a bug to do it, I'd say keep it private as a lot of people don't read the forums and might fall prey to this bug unknowingly, which half the population now knows and the other half doesn't. A person with a bug report on such things needs to think about posting publicly and real damage it can do.
Note that if I see something posted that really does cause potential problems, I will most definitely move it to a private forum if it is posted publicly.