Margins change depending on title visibility

I have been annoyed because the margins around my article change, depending upon whether or not the title is displayed.

I haven't figured that out yet, but I did find a work-around for my specific problem.

Here's why I have been hiding article titles:

I have a category blog at the bottom of each page to show a list of upcoming events. The blog entries are articles, of course, and they have a one-liner introduction followed by the readmore. I need the introductory line for the blog listing.

However, since the actual title of the article and the introduction are likely the same, or similar, if they both display then it would look like the same text, twice. I don't want that, so I've been hiding the title. (That also lets me put a little tag, of sorts, in the title.)

Hiding the title buggers up the margins around my article.

What I've discovered is that there's another way to accomplish what I want: Instead of hiding the title, I can hide the introduction. I never paid attention to that option, but what it lets me do is flip the whole thing around. The line before the "readmore" is not displayed anymore, so I can display the title without getting redundant text.

Displaying the title restores the margins.