Some prompts are incredibly vague and open ended... By that standard, you could end up having to ask about an awful lot of stuff.
I think the responsibility lies on both parties, one to state their DNWs and even things they would prefer not reading; one to ask if they are uncertain about something(which realistically speaking isn't going to be 'check every single thing that isn't mentioned in the prompt') and both to be sufficiently grown up about it to realize that not every thing may be presented or received in the way each party would prefer.
That's not to say a prompter shouldn't be squicked if the writer takes a sharp turn off into NO Way in Hell Land, but they should recognize that these things happen. If the writer includes something the prompter specifically said not to, then the prompter should let them know because that is rude.
Re: Fills getting weird
I think the responsibility lies on both parties, one to state their DNWs and even things they would prefer not reading; one to ask if they are uncertain about something(which realistically speaking isn't going to be 'check every single thing that isn't mentioned in the prompt') and both to be sufficiently grown up about it to realize that not every thing may be presented or received in the way each party would prefer.
That's not to say a prompter shouldn't be squicked if the writer takes a sharp turn off into NO Way in Hell Land, but they should recognize that these things happen. If the writer includes something the prompter specifically said not to, then the prompter should let them know because that is rude.