Honestly idk why anyone that was familiar with FX was trading CHF when that took place. It was basically the same as taking a EUR position, except EUR had better spreads and more liquidity. It would be like trading something pegged against the dollar instead of USD itself. Why? Not only that those that new about the EUR and CHF new it wasn’t a true peg either it was a price floor set up to prevent CHF from becoming too strong, they would’ve allowed it to weaken. The fact that it stayed pegged kinda told you that CHF was fundamentally way stronger than its rates showed. Further if you’re an options buyer the max loss is always defined, as a seller it’s a different story, unless you hedge the position, example credit spreads(which has a defined max loss also). If you’ve found a buy strategy that works or a hedged sell strategy that works I wouldn’t worry about the strategy. As for the broker I can’t specifically speak, but only imply that if you’re practicing a defined risk srategy with options I don’t see how your losses could exceed that regardless of broker.
The EURCHF incident was a Black Swan Event. Black Swan Events are impossible to predict, but easily explained in hindsight. Hindsight is always 20/20.
With options selling, the only way to assure you won't blow out is to sell with little or no leverage. An SPX put with a strike of 2000 has an aggregate of $200k, so if you sold 5-6 in a $1MM account, you will never ever blow out... even in a 1987 crash. But your annual ROI will be 0.4% plus the Treasury rate. Which is why no one does this. The ROI comes from leverage; so too does the risk.
I guess some people are informed before hand and some after. The event and the timing itself wasn’t predictable but the fact that it was a floor and and not a true peg was obvious before hand. SNB made that clear it was protecting appreciation of CHF it wasn’t a peg but a floor. EUR/CHF was allowed to float up but not below 1.200 It was well known to anyone that paid attention. I took CHF off my watchlist. Since EUR/CHF was always pretty much pegged to 1.200 it was an indication that it was really stronger than it’s spot rate. Go look at a chart and tell me it didn’t trade like EUR. If it’s pretty much on par with EUR wouldn’t the smart play be to trade the more liquid and lower spread of the two. None of that was hindsight.