Firstly, I guess you might save yourself a few KB.
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Maintainable CSS
Reuse and DRY are such important principles in software engineering but when it comes to CSS, it ironically makes maintainance harder. Avoid trying to reuse style rules and gain the benefits of easy to maintain CSS.
What if I really want to reuse a style? It is extremely rare, but there are times when it really does make sense to reuse a style. In this case use the comma in your selectors and place it in a well named file.
Because visual class names don’t hold much meaning. Take red. Does this mean a red background? Does this mean red text? Does this mean a red gradient? What tint of red does this mean?
Because reuse makes debugging more difficult.
Don’t try and reuse styles. Adopt a duplication-first approach
Semantic class names are a corner stone of MaintainableCSS. Without this, everything else makes little sense. So name something based on what it is and everything else follows.