It’s a bit difficult to tell you the exact CSS code without seeing the actual HTML code of that section.
Now we have 2 ways:
1. Do it yourself (see below).
2. Tell me your website so I can tell you the exact CSS style.
Basically all you need is to find a unique class or ID that is wrapped around the secondary title so that it’s only being displayed there and not anywhere else.
If you’re using Google Chrome as a web-browser, right-click on the secondary title in the section you want to disable it in and chose “Inspect element” (or similiar; I’m using a German version) on the bottom.
A window should be displayed on the bottom of your browser containing the HTML code with focus on the selection.
Here’s a screenshot of an example how it’s supposed to look like. If I wanted to prevent the avatar from being displayed, for example, I’d use this code:
.threadauthor .avatar-48 {
display:none !important;
}
Note that the !important attribute may be necessary as it makes the browser to use your code over the default one.
I hope I could help a bit.
