@Travis In Austin, the marketplaces on reddit are pretty strict. Usually a post requires strict title formatting such as this..
Title must be formatted [WTB/WTS/WTT][Location][H] Something [W] Something
Example: [WTS][USA-NY][H] Marantz SR7400 Receiver [W] PayPal, Local Cash $150
You must include pictures in sales and trade posts. At least one of them must have a proof/timestamp. Proof/timestamps must include a username & timestamp matching the username posting and date posted.
All haggling and such is limited to DM's. Post chatter is universally frowned upon except for:
Clarifying something about the item, such as accessories included or maybe the seller forgot to mention a product version which might impact the sale, etc.
On reddit, scammers can be banned from posting in a section but still view the listing and still DM members. So they require everyone to add a quick comment indicating that a PM is forthcoming as proof that they're not banned from reaching out. I think the inverse is true here where PM's can't happen until after X number of posts, so this step may be unnecessary. Maintaining a pinned list of known scammers or something might help on this front.
And then there's usually a confirmed trade list/count where buyers and sellers simply state that User1 sold/bought/traded X product with User2, and User2 confirms.
Price check threads are allowed by using [PC] Item you want to price check, and this is where people are encouraged to chime in with current market trends, etc.
Non-compliant posts are simply deleted and a message is sent to the user to recreate and correctly adhere to the prescribed format.