"You defeat the purpose of this forum."

As noted, when you update a topic, it would move to the top, as the sort order is most recently updated. Not most recently created.

"Not sure who give the authority to mark as duplicate"

Well, that would be at Intuit's request and direction (they provide the tools), and the peer users volunteering to be helpful try to be helpful.

Making it easier for your peers to help means not making it harder. More than one topic on the same issue scatters the replies and if nothing else, I politely put a link to the original, so that anyone stopping in here to try to help, knows where you already have content and previously started the same issue.

Don't think of this as a prevention. Think of it as traffic redirection.