Humorous:
* As sure as a comma's place is a mystery, ...
* Like a comma in a crowded sentence, ... (implies being lost or easily missed)
* Where the comma reigns supreme, ... (plays on the comma's role in grammar)
Serious:
* Because a comma can make all the difference, ...
* Since commas guide the reader's eye, ...
* While commas may seem simple, ...
Creative:
* As if a comma were a whisper in the flow of words, ...
* Like a punctuation mark's silent dance, ...
You can choose the phrase that best suits the tone and context of your writing.