If you use and customize Vim a lot, your .vimrc file tends to grow rather quickly, and it's important to make it easy to navigate. If you ever take a break from working with your .vimrc and come back later, you'll thank yourself.
Comments are crucial for making sure you remember what's going on. If you take just one thing from this chapter, make sure it is comments. Just like when working with code, comments save you wasting time trying to understand what's going on.
I try to make a point of documenting every configuration bit with a corresponding comment:
" Show last command in the status line.set showcmd" Highlight cursor line.set cursorline" Ruler (line, column and % at the right bottom).set ruler" Display line ...