All "buyer only" ID's can only show 100% since it's been impossible to leave a buyer a neg since spring 2008.
You can block buyers that have received 2 UID's in 12 months under your "Buyer Requirements" settings...and continue to aid fellow sellers by completing UID's on future deadbeats so that block may help them too.
Do not attempt to leave a negative comment using the green dot (+) you're limited to utilize for leaving FB for buyers. If you do and the buyer reports it to eBay, then you will receive a seller violation "strike" against your ID.
"They don't keep me here 'cause I'm GORGEOUS, they keep me here 'cause I'm SMART"...Judge Judy