Feature Request: Ability to rate users who contact sellers... and never show up.

Level 1
Hello OfferUp,
I have been using your service for the last month or so and it seems many people just want to negoiate lower prices messages endlessly...but never actually show up to buy the item.
It's great we can rate people who we buy/sell from - but it would be nice to be able to rate people who message sellers too. Common courtesy is in short supply.  If people knew they would be rated for no shows, back and forth messaging and negotiating lower prices and then never replying back - maybe they would act with more compassion.. or at least other sellers could rate them and give the rest of us a heads up that a particular user is a flake.
If we had that ability, I think it would drastically cut down on the number of people who just seem to enjoy negoiating lower prices with no intention to actually buy anything.
I do ask people if they are ready to "buy today" before negotiating.. but the fact that we need to even do that shows how much of an issue this is...  if we could just rate people who make "offers" to sellers it wouldn't be necessary to ask "if they are ready to buy" in the first place - we would know they are serious.
The "no shows" and endless messaging needs to be addressed. 
Thank you so much for your consideration.
Level 7
Sounds great, but just like any rating system it could be abused (e.g frustrated seller gives low rating to someone who asks questions,but not ready to buy yet. ) Yes,we need a system, but one that works fairly where there are safeguards in place so no one gets an undeserving bad rating. As for people obviously trolling, this would help other people not waste there time with them. Hopefully putting an end to the endless trolling on this site. That would be a dream come through.