Please clarify which category or threads to post in

Some questions about posting, especially comments on the PUP:
-If we have a bug in the PUP, should we put it in the mega thread or in the bug category?
-If we have feedback suggestion while using the PUP, but the issue is not necessarily one of the changed features of the PUP, should we put it in the mega thread or just make a note to the devs in the general discussion area? e.g. If there is a thing we thought would be in the PUP, but is still kind of broken, where do we put that?
-If there is a loophole kind of issue that is not really a bug, but may be unintended, is that something we should be in the bug category, or just the general discussion category? e.g. Someone maybe wants to mention the “trade trick” kind of issue, which not really a bug.
-In the PUP mega thread (or any thread really), if there is comment that is related but not exactly the same as my comment, is better to reply to their related comment, or just reply to the O.P. of the mega thread?

Thanks for the clarification.