The purpose and frequency of punctuation use has fluctuated drastically over the past few hundred years. Its most basic use was to demarcate pauses that may not have been obvious otherwise. That basic function is sometimes overlooked in the blur that is our modern world of hashtags, exclamation marks, and emojis. But punctuation’s power to control time and rhythm has not diminished in the least.
Take these two examples:
The man, weary from a long day, labored down the hall and, finally, collapsed on the bed.
The weary man labored down the hall and collapsed on the bed.
Which example took longer to read? Probably the top one. The commas act as small speed bumps, slowing your eyes as they read from left to right. Sometimes, we as writers want to slow the reader down in order to prepare him or her for an important moment.
The door, rusted over with time, slowly creaked open (as Tom watched, horrified) before a slimy, gooey hand reached in — and grabbed him!
That probably will have more of the desired effect than: The rusty door opened to reveal a slimy and gooey hand that grabbed him.
Whether employing a heavy or light use of punctuation, simply be aware that it will affect the readers’ experience