I think it's generally a good idea that all trainees can see the other trainees question threads, as pointed out they will possibly benefit from the other threads as well as their own. Also for the sanity of the mentors it should help prevent having to answer the same questions time after time.
I don't think it would be necessary to have another forum to cater for private questions, hopefully there will be an environment in this particular forum that there's no such thing as a stupid question and all questions without exception will be answered without the quips and remarks they often tend to attract in the main forums.
One thing that might be nice is some sub forums in here to categorize the questions. Maybe one for general electrics, one for formulas and mathematical questions, one for rules and regs, maybe even a separate chit-chat area just for trainees where anything goes.