I've noticed over the years that, not just on Buffy, but with all of her roles, Sarah seems much more comfortable with scenes where she cries than with scenes where she should be laughing. Even in funny scenes, she is almost always the "straight man" rather than the one who delivers the punch line.
None of the others seem to have that problem. David, in all of the bloopers and out takes that I have seen, is an absolute clown, and everyone else seems to have their funny moments, gags, or just laughs at their or someone else's flubbed lines. Maybe Sarah just doesn't consider that as professional behavior, or maybe it just never was captured and preserved on tape.
When you see her interviews she isn't much of a joker either. She is much more with the sarcastic quips than anything else.
Anyhow, Sarah seems to do far more crying than anyone else in the Buffyverse.
In fairness, that makes sense. She is the central character, it's about her life and she is our lens. It wouldn't really make sense for anyone else to carry the real emotional weight. Of course the Scoobies have taken their hits, but ultimately, it's Buffy who takes the hurt.
Tome
Agreed.