I feel like one of the things that makes a difference is whether the person was important enough as themselves or if they're just a symbol. And while Jason was somewhat of a symbol, I feel like there was enough of the actual personality to make it more than just a simple fridging? Or maybe the fact that you had all these other characters who also had to think about how they felt about him (and since some of these people were also Robins that put them on the same level). Plus the fact that Jason was killed following his own story with his mother etc.
And then he was brought back anyway, mostly it seems because there were writers who were interested in Jason the person and not just Jason the symbol for Bruce.
But still I do think that sidekick definitely stands in for chick often in comics. Robin was constantly getting kidnapped and tied up and put in peril for Batman to save.