Hardcore Unwritten Rules

I was wondering if someone could help me with the unwritten rules of hardcore minecraft. I want to start a world, but want to go in knowing the unwritten rules.

So I see lots of users using TNT dupes and falling block dupes, and this seems to be acceptable. I'm guessing the same acceptance wouldn't be applied to item dupes like diamonds and netherite?

It just seems like some glitches are allowed, whiles others are frowned upon.

Let me know your thoughts.