This is a great thread, but I have to admit I only made it through about 2/3 of the posts. It's just so long! I hope this post acts as a bump so more people can experience this "entertainment"
I either haven't witnessed anything really gross, or have just totally blocked it out. I have a feeling now I will notice everything!
The one thing I see all the time though, in WDW and elsewhere, is people who leave their tables FILTHY. I don't expect people to wipe down their tables with a clorox wipe when they're done, but have the decency to try your best at cleaning up the food explosion that apparently occurred at your table. At a busy QS restaurant where you sometimes only have 1 table to choose from, it's frustrating and gross to have to clean up someone else's mess before you can put your food down.
Also, a note on those automatic flushing toilets. Anyone else paranoid that they won't flush when you leave? If mine doesn't flush by the time I am ready to exit the stall, I always push the manual flush button. I don't trust that it will work when I leave!
And one last story that I just remembered, but not WDW related. When I was very young (5? 6?) I was food shopping with my mom and suddenly had to throw up. I told my mom and she frantically asked around for where the restroom was. Of course, it was upstairs in an employee area. We rushed up there and made it into the bathroom, only for me to lose it right in front of the stall. As gross as it is, I am completely empathetic to parents who have to deal with sick kids.