No, the opposite. A documented post-mitigation report showing levels below 2.0 pCi/L is a selling point. Untreated high-radon homes lose ~$5,000-$10,000 in resale value or stall in negotiations.
More detail
Cincinnati MLS analysis shows two effects of documented post-mitigation: faster days-to-close (median 8-12 days faster than comparable unmitigated homes in the same zip code) and lower likelihood of price renegotiation during the inspection contingency. The dollar value of the mitigation system in resale is roughly the cost of the system itself plus a small premium ($1,500-$3,000 effective increase in offer prices on average). Homes that test high during a buyer's inspection and have NO existing mitigation typically face one of three outcomes: seller credit equal to the cost of mitigation (sometimes more), seller installs before closing, or buyer walks. The "buyer walks" outcome is rare but does happen, particularly with FHA-financed buyers who are risk-averse. Listing pre-tested-and-pre-mitigated removes that contingency from the deal entirely. Cincinnati market context: in Hyde Park, Mariemont, and Indian Hill, documented mitigation is increasingly a buyer expectation rather than a bonus, particularly for pre-1950 homes. Listings without mitigation in those neighborhoods either sell with a price reduction or become harder to move. In newer subdivisions (Mason, West Chester) where most homes test lower, mitigation is a smaller resale-value factor but still favorable.