Albeit, I'm still relatively new here, BUT
If something is being sold here which they've assigned a grade to which is obviously WAY off base (say a VF that's trying to be passed off as an AU) then I have no problem with anyone bringing attention to that in the sale thread. If it's just questionable (AG being passed off as G) then not so much... maybe a PM to the seller if anything.
In fact one of the things I LIKE about the sale threads here is that it DOES happen, both to the benefit and detriment of the seller. Whereas on
ebay there's no ability to view raised questions. If the coin IS what the seller says it is then they should be able to easily post WHY the coin is what it says it is. A well written out reply can actually lend MORE credence to a sellers listing.
In fact I've quit selling coins on
ebay because of the BST forum here. I will only sell on CCF even though I know I would very probably realize a higher sale price
ebay (take for instance my 09S Lincoln that's currently for sale... I know I could
ebay that one for more than it's going to sell for here). It might sound stupid, but I feel better about passing on my extras and whatnots to CCF members because I KNOW that they're collectors trying to learn or trying to teach.
To me CCF is first and foremost a place to learn. I've done a ton of it here in regards to Lincolns with the explanation of Coppercoins and BadThad. I welcome their comments in ANY thread on Lincolns be it a BST thread or somewhere else. To me the BST threads are sale threads BUT primarily they're still a place to learn, be it the seller or someone else.
Maybe I'm way off base here...