[rimantas]

  .homer #left-eye

This indeed makes (almost) no sense. It makes no sense for sure if you intend to have several characters on the page — id must be unique, and it does not matter that something is in front of it.

.some-class #some-id makes sense only if you want to style page-unique elements differently in some cases but even in that case I'd argue that #some-page-id #some-id would be better (assuming #some-page-id is the body element id).