Richard Cory commands attention. He is regal and graced in all his glory. When he simply speaks good morning, he flutters pulses. The people's hearts flutter when he speaks something as simple as a good morning:
And he was always quietly arrayed,
And he was always human when he talked;
But still he fluttered pulses when he said,
"Good Morning!" and he glittered when he walked.
The people are in awe of Richard Cory. They hold him in high esteem. They long to be just like him. They are astonished and fascinated by his riches. They think he is everything a person could wish to be:
...we thought that he was everything
To make us wish that we were in his place.
Just seeing Richard Cory causes the people to long to breathe in his graces. That is why their pulses flutter. Richard Cory makes such an impression on the people until they are enraptured by his presence. He is schooled in grace and charm. He causes the people's hearts to beat a little faster. That is what is meant by his ability to flutter pulses.