Don't know that I've ever seen anything on this topic so thought I would start a thread--though mine always seem to unravel (that's supposed to be funny).
At the top there are 4 tabs: Discussions, Categories, Search, Account
If you click on Search there is a very simple option presented that is helpful, but not too much.
Click on the "advanced" option on the right side and you have more choices. For example, you can search for a word in the comments when the poster was a particular person. Or, you can search for a particular word in the comments or subject (topic).