Breathe a bit newbie.
He's not asking if hearing people accidently use LANGUAGE (word/sign with meaning) ... he's asking if hearing people accidently create a handshape that happens to be a sign while they are gesturing.
A common example would be hearing people putting their hands together while talking and accidentally making a gesture that in ASL means "VAGINA". They aren't intending to sign anything, they aren't applying any meaning - heck half the time they aren't even intentionally gesturing - but none the less they (through chance) have formed a handshape that happens to be something in ASL.
Things like this happen all the time for multi-lingual people - we hear/see a word in one language that also means something (though something completely different) in another. We "catch it" because we happen to know the meanings in both (etc) - however that doesn't mean the person using the word intentionally chose the word for that purpose - its just an 'accident' of sound/sight.
P.S. In case your rant was directed at me:
A) I'm not hearing, I'm Deaf ... I'm fluent in ASL and English.
B) Linguistics is something I've studied quite a bit of - so I wasn't mis-speaking.
C) If you're going to make a point of criticizing people's understanding of word/sign & English/ASL language usage - take the time to use spell & grammar check on your posts first so you don't look like a hypocrite