Extra non-breaking space in excerpt

The shortcode I am using in the widget:
[catlist post_type=newsletter_excerpt numberposts=1 excerpt=yes excerpt_size=20]

And, it’s not a manual excerpt; it’s just the content.

Looks like a CSS issue. The text is cramped in the widget due to the widget’s width.

You can try something like this:

.lcp_catlist li{
  font-size: 0.99em;
}

This makes it look good on Firefox, maybe try some other font sizes or width which may help the text have more space to avoid the breaking lines.

That is interesting; it does seem to work at that font size. I’ve experimented with other sizes and it really does have to just be smaller. Which of course alters the design somewhat.

I wonder why &npsp; is getting inserted?

You’re right, I hadn’t noticed the   character being inserted. Did you check the “text” view when editing the post? Maybe it’s being inserted by WordPress somehow when saving the content.