I typically commit at least once an hour when I'm coding full steam ahead. My rule is I commit to my local repo whenever I have uncommitted work that I'd care about losing (if I made a blunder and had to revert everything). I also commit locally whenever I switch tasks (so one commit is one coherent block of work). I only push from my local to central repo when I have the code in a reasonable "working" state.

If you're working on your own then commiting frequently is fine. If you are working with a team then that's a lot of information for your colleagues to process, so it's a good idea to condense your changes down a bit when you commit to the main branch. I think that's what the article is getting at when it talks about feature branches.