LESS vs CSS

less.css

/* less file */
.my_mixin {
	display: block; 
	text-indent: -9999em; 
	background-color: transparent; 
	background-position: 0 0; 
	background-repeat: no-repeat; 
	overflow: hidden; 
}
h1 a, .pagination em, .cog a { 
	.my_mixin
}

/* css file */
.my_mixin {
  display: block;
  text-indent: -9999em;
  background-color: transparent;
  background-position: 0 0;
  background-repeat: no-repeat;
  overflow: hidden;
}
h1 a, .pagination em, .cog a {
  display: block;
  text-indent: -9999em;
  background-color: transparent;
  background-position: 0 0;
  background-repeat: no-repeat;
  overflow: hidden;
}

Oh I see what you mean now, like:
http://stackoverflow.com/questions/7557626/less-js-redudancy-in-css-use-of-mixins-instead-of-selector-inheritance

The above post makes me want to try out @extend in SaSS/Compass:
http://awardwinningfjords.com/2010/07/27/sass-extend-introduction.html

Yes!! Me too. Seems to solve the problem