Yes, it's true that people only usually apply the word to a more restricted subset of things than those which won't kill the eater; but such a behavioral tendency should not be confused with the actual semantics of the word.
To claim that the actual semantics of a word can be defined by anything other than the behavioural tendencies of its users is, at best, highly controversial. Whatever you or I may think, "irregardless" just is a (near) synonym for "regardless" and, to judge from my own experience (and the majority of comments from native speakers on the thread) "edible" actually means "safe to eat" (although, as Alicorn says, it's a little bit more complicated than that).
Words mean exactly what people use them to mean - there is no higher authority (in English, at least, there isn't even a plausible candidate for a higher authority).
To claim that the actual semantics of a word can be defined by anything other than the behavioural tendencies of its users is, at best, highly controversial. Whatever you or I may think, "irregardless" just is a (near) synonym for "regardless"
I'm advisedly ignoring the original context, but I'm curious about the idea that your behavioral tendencies in particular (and mine) with respect to the usage of "irregardless" don't affect the actual semantics of the word. At best, it seems that "irregardless" both is and i...
Here's the new thread for posting quotes, with the usual rules: