[abbr] tag only sometimes works

Refer to My blog, specifically the first and 2nd posts. Notice the word IE in the 2nd post, formatted with an <abbr title="Internet Explorer">IE</abbr> tag. In the first post, NSFGS is similarly tagged as “Not Safe for Grad Students,” and if you go to the full page for that post via read more, comments, etc., you’ll see it works correctly there.

You can also view source to see it’s correct.

I’m baffeled.