Font settings stick at Exceprt point

At present, I’m using Excerpts on the blog page.

If the text in a blog post happens to be italic or bold at the point where the Excerpt begins, it turns everything after that into bold or italic, including the sidebar.

It’s also progressive. If, say the third post excerpt label hits Italic text, all else is Italic after that. If the 5th post is bolded at the excerpt point, all else after that becomes bolded as well.

You can see the effect on the second page of my blog. Click the Blog tab, then page back one. Notice how the sidebar is now all italics. This effect begins on the third post. Page 3 has the same issue, also from the third post. Page 4 gets it on the 4th post. Page 5, near the bottom. Page 6, the second post.

And so on. In other words, the sidebar and many of the post summaries do not display as intended. A fix for this would be appreciated.