For me its when waiters walk up to your table when you are waiting for the food and place dirty dishes onto your table (sometimes even with a smile) and then walk away. Happens at least ONCE for every Sim I take to a restaurant. Never so happy to see that I can enter build to remove the dishes.
When Sims are sitting together, at a bench or at the chess tables, flirting up a storm and a stranger or even a friend (to either or both party) comes up to them and just stands there staring at the two listening to the whole thing doing nothing. At least with the Feng woman she scolds them, but the others just stand there staring at the love birds with that creepy Sim smile.