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.
In the second stanza of the poem, the speaker states that Richard Cory "fluttered pulses" whenever he spoke. On a literal level, this means that when Richard speaks, he excites people to the point that their pulse rate increases. Even a simple phrase like "good morning" is enough to make ordinary people experience this intense sense of excitement.
On a deeper level, however, this phrase is critical in the portrayal of Richard Cory as a man who is both important and superior to those around him. This portrayal begins in the first stanza when the speaker comments that Richard Cory was a "gentleman" who always attracted the attention of the townspeople. In other words, Richard Cory is so interesting and so glamorous that those around him are awestruck. This explains Cory's ability to flutter their pulses: people want to be near him and to be like him. It is as though these townspeople have a crush on Richard Cory.
This means that when Richard Cory comes saying" Good morning " , the speaker's heart beats rabidly.