Feedback loops are chain reactions. When we say "feedback loop" in the Founders Notes, we mean that the underlying security is far enough away from Zero Gamma (the inflection point of positive and negative market gamma) in either direction that chain reactions are more likely. Also, feedback loops are more easily triggered in negative gamma regimes (where market gamma is net negative), since realized volatility (the expected percentage move for a period of time based on historical data and with 68.3% confidence) is expected to expand more violently during these times, which means trends can more easily run away with breakout momentum. 

Colin Bennett addresses these chain reactions in Trading Volatility, “[If a] trading desks’ volatility short position has now increased, they have to buy volatility to cover the increased short position, which leads to further gains in implied volatility. This starts a vicious circle of increasing volatility” (2014, p. 87). Essentially, there is a cyclical momentum which takes place due to continual hedging (portfolio rebalancing done to neutralize risks) that needs to be done by short option holders as those short options increase in size. Especially to the downside, partially from vega (the sensitivity of a price to implied volatility) expansion.