Beyond the basic happy smiley and maybe the wide-eyed oh-shit smiley I have no firm idea of what the others mean, and AFAIK no way to find out.
It isn’t communication if your audience doesn’t know the terminology you’re using.
A hundred years ago you could send somebody 3 white lilies and 2 yellow daffodils and they’d know what it meant. They could write a whole paragraph about the meaning of those particular flowers in that particular combination.
Who here (including me) has the slightest idea now what that meant then?
Back to smilies, they’re mostly harmless noise. They’d be a better tool for communication (the point after all), if the posting page provided a textual explanation next to each icon, so our collective usage would converge towards a common standard.
I just found out from AskNott that you can hover over a smilie and see the “official” meaning. I’ve been here a year and I never knew that; I bet the majority of posters that use them heavily have no clue what the official meanings are either.
My bottom line: they’re silly things for silly posts. For some folks, thats a good fit. For others, not. But I sure wouldn’t want the SDMB to kill them off; it’s reactionary conformism to want to eliminate something just because it doesn’t match your taste.