If you assign priority, the process is no longer random. The priorities are added to a list and sorted - apparently in a stable way, i.e., not random.
It's not like WL4 which, as I recall, essentially gave a pseudo-random result by
numerically sorting on the symbols, which ended up favoring symbols in a mixed-alphabetic sort of way.
QUOTE:
How do symbols get selected anyway in WL6 if Priority matches (like in my example or by accident on two or more symbols)?
It would depend on the List<> sorting algorithm, which you can probably find by digging through msdn a bit.
Assuming you found out, how could you use this information? I mean, if you assigned the same priority to two or more symbols that had to be purchased at the same time, but you didn't have enough money for all of them, what would you do in real life? Would it matter which one was purchased? If it does, then you should be able to add more logic to your priorities to ensure uniqueness.