I don't report listings anymore, because I agree with BB that I hardly see any reported listings removed. In the rare case that a listing is removed, it's for an extremely bad fake with a well known counterfeit serial #. This has made me believe that none of their authenticators actually review any of those reported listings and that that job is passed on to the Posh community when those listings make their round in the "Help keep Poshmark in tiptop shape!" requests.
And I bet lots of members won't review at all, and if they do, they'll just pick the "not sure" option to be on the safe side. That's what I do if I see reports of brands I'm totally not familiar with, or brands/items I know well, but yet not enough to be making an authentication call. I personally believe that this is the reason why so many scammers are flourishing on this platform and sometimes authentic listings are taking the brunt: because Posh's authenticators fail to do their job and pass it on to members who most of the time, don't have a clue. I don't believe Posh gives a damn who gets scammed as long as it doesn't get them involved and their pockets are filled.
I've never called out any item fake in an actual listing, but have many times let a (potential) buyer know on one of their listings, or privately, by using the "add to bundle" feature. I've had scammers found out about this and consequently went berserk on my listings, but I never let that get to me. By flagging their comments they are removed from my listing instantly.