And just to keep complaining...
People often don't get schooled in music etiquette. Not just getting up during a performance, but talking. I think they're so used to "canned" music, they don't know how to act around humans on a stage. They maybe dream of a "pause" button.
They also don't want to work at editing their own post before sending it (whoa-whattaconcept), but I suppose that's a bridge too old school.

Of course, maybe the getting up is a matter of bladder (or other) imperatives, and nobody else can really judge how badly someone else needs to pee.