In the top left-hand corner of your screen when looking at the blog, you should see a text box with a magnifying glass. This allows you to search the blog by keyword, but note that this tool only searches original posts, and not the follow-up comments.
Therefore I'm maintaining an up-to-date list of labels for each post including topics discussed in the comments. In this way, the label system will be the most useful tool to search the entire blog including the comments. The list of labels is found in the right side-panel underneath the Blog Archive.