How to comment in Vim's config files: ".vimrc"?
A double quote to the left of the text you want to comment.
Example:
" this is how a comment looks like in ~/.vimrc
"This is a comment in vimrc. It does not have a closing quote
Source: http://vim.wikia.com/wiki/Backing_up_and_commenting_vimrc
Same as above. Use double quote to start the comment and without the closing quote.
Example:
set cul "Highlight current line