aristotle - 1:39 am on Mar 4, 2013 (gmt 0)
I almost never use boldface on isolated words within sections of content. If the content is well-written, the reader will be able to recognize important words without any extra help.
Also, I'm wondering why you're considering using boldface only on keywords. If you're going to use it at all, why not use it on all important words, not just keywords?