A low MFI reading below 20 is not always a buy signal; it flags oversold conditions but does not guarantee a reversal. MFI can become oversold below 20 and prices can continue lower when the downtrend is strong, which is why Quong and Soudack recommended expanding these extremes to further qualify signals.
A reliable bullish failure swing forms when MFI becomes oversold below 20, surges above 20, holds above 20 on a pullback, and then breaks above its prior reaction high.
Confirm with divergence or support before acting.