Bolted lettuce is famously unusable because your sweet salad leaves turn bitter.
But does the same apply to spinach? It's a lettuce type crop (and equally prone to bolting in hot weather) but it's basically a bitter leaf anyway and typically cooked to a mush (a nice mush, if spinach is your thing, but still a mush) anyway, so does it really matter if additional bitterness has entered the plant?