"extra nice", eh? Labrat, I'm sure that you didn't mean this to sound as diminishing of both those writers who care about the feelings of their readers as well as those readers who, for all sorts of valid reasons wish to avoid deathfics.
In the interest of balance perhaps you might call those writers who chose not to include a warning as "extra mean"?
Um, no, I think those who choose not to include a warning would be called "normal"

Sorry, but most of us here are grown-ups who take responsibility for our choices in reading. Authors aren't required to explain their stories advance. If they choose to, it can be seen as "extra nice" -- but that by no means implies that to leave the warning off is any kind of mean.
PJ