Able to search but not comment

Hi there.
I need some step-by-step guidance on the following:

How do I remove everything from the content itself on a page, and still keep the possiblity to search the entire site? By this I mean the comments-field and such. (I stumbled over a thread which made me believe the two effect each other?)
I want to keep the search-field, but I want my visitors to be able to perform an advanced search.