Exactly. Just name a few examples of volatility change.The issue is the volatility...its not the popularity or lack of such involving the technical signal. Simply, the volatility will still impact technical signals not popular or custom designed (nobody else is using it except for that specific trader).
In October, a season trader would have noticed the increased speed in the price action, increased speed in profit targets being reached, increased speed in stop/loss protection being hit, increased number of no fills, increased number of trade signals, unusual profits, unusual losses and many other unusual things that a season trader should have picked up on.
Also, I think traders using a technical signal only for a couple of months will be more jumpy or less complacent when October showed up in comparison to someone using the exact same technical signal for many years. Thus, the less experience one has with a technical signal...the faster they are going to abandon it and look for something else at the first signs of trouble.
I'm sure months like October to the first few weeks of November taught many valuable lessons...primarily to pay attention to volatility analysis regardless to what type of a technical signal/pattern someone is using...at least it should encourage many to look at their backtest results to see how their technical signal performed in high volatility trading conditions.
The results of looking at the historical performance they can exploit it the next time unusual high volatility conditions show up in the markets or at least stay on the sideliness if their backtest results show poor trading during high volatility conditions.
wrbtrader
CAT - Jan 2018
CBOE - Feb 2018
AMED - Oct 2018
ABMD - Jul 2018
TTGT - Aug 2018
DJI - Feb 2018
Just do a frequency plot (bar chart at 0.5% interval) of the absolute value of % daily change for the above before and after the dates. One can clearly see the "after" charts have fat tail.
DJI plot from my other post.