As much as you can try and lock down a forum and add as many hoops as possible for a scammer to jump through, someone who knows they can get free money from people will become an athlete at jumping through hoops.
The best defence is you becoming suspicious of absolutely everyone you don't know personally.
If someone came up to you in the street and said they would give you a watch in 3 days of you gave them £200, would you hand over the cash, no of course you don't, but some people do, that's why this guy is sending everyone a Pm because 1/10 people will bite but wouldn't you feel a bit more comfortable knowing that money has a string attached to it and if things went sour you can pull it back?
That's what PayPal goods and services is....
I don't know how many times I've seen posts from people saying they sent some random person money through friends and family or via bank transfer because the seller wanted to save on fees, those fees are there to protect you... Not them
I don't wish to toot my own horn or jinx it but in the 20 years I've been playing and the 700+ guns and countless bits of equipment I've bought no one has ever scammed me but maybe that's because my due diligence is so high, before I send anyone money I read their full profile, I scan all their posts, I see what guns they've sold in the past, I read all their feedback, I see how long they have been in the site, I try and find their Facebook profile..... I want every single bit of information I can find before I hand my hard earned money over to a stranger and if that person is new to the site but genuinely might have that product, I'll ask them to take a photo of the item with them holding a can of spam.... A literal can of spam, you want my money, go buy a can of spam, is that over the top? Maybe but it's my fucking money
(this came up from a car forum over 15 years ago, guy claimed he had some super sick car and no one believed him and someone threw out this stupid idea to hold up a can of spam next to his car and he did, forum blew up, spam photo became a thing to prove said item was yours)
Scammers will always come and go, you'll never get rid of them but please do everything you can to cover your arse by using G&S