~snip~
First I can't stop laughing at the Huge Member - to good.
I'm not surprised it's been thought of, you tend to find a lot of the opportunities for improvement. It just came to me while navigating a few hardware threads where there was confusion about distributors. The local rules and sales/auction threads were a bit of an afterthought for me, but made sense that this is a feature that could be useful in multiple ways.
If the feature was to be implemented, It should also be limited to some specific boards as I see a situation were some users might misuse the feature as advert opportunities (i.e selling the pinned message spot to advertisers) I do observe same issue with platforms like Facebook and telegram with this feature.
I'm not really worried about the sale as an advertising spot. The same rules would apply to being able to put an advert in your OP, which is available but limited. More people may try to just use this feature, but I would advocate for it being disabled for varying lengths of time if abused.