Then, I started inserting videos and larger screen shot images to illustrate instructional material. They would bridge across columns, creating a really ugly site with poor usability. It was a theme-specific problem, but it could definitely show up in others. However, the cure for it is a plugin that has some great features for anyone wanting to use excerpts with some formatting ability.

The plugin is Excerpt Editor, and it solved all of my problems, plus gave me some flexibility I didn’t expect.  Once installed, you have numerous setup options, including how many characters of text to use from the beginning of the post for the excerpt.  Check it out.