Here's the heart of the matter, which you both should've seen right off the bat:
We don't speak English. Not Webster's English, not the Queen's English, and not American English. We make up words, we use them in the wrong places, And many of us don't spel none to good, neither.
We can understand more than Webster would like to believe, plowing through metaphors, typos, bad grammar, and much much more. When 'we' say that X is not a word, we mean, "We don't like it. Please use something else". We probably don't mean that we don't understand.
Slang is a good thing. Ask Webster 1913 what Cute means. Or internet. 'Downvoting' may not be a word, but Webster 1913 wouldn't admit to 'TV' or 'quark' either. Webster 1985 doesn't recognize internet, although it does have internode, a word which I have never heard used.
Maybe the best measure of what is a word for this population (E2) is what is noded. Downvote does seem to be a word for us. It seems that many 'noders' agree on this.