What's going on with illustrator character tracking?

Hi everybody.

Today, while working on something, I tried to apply some tracking to some text to spread it out more. The problem is that the character "f" seems to be conjoining with certain other characters (eg: ff, fi, fl, etc.). Can anyone shed some light on what is going on here? It seems to happen with only certain typefaces, so I believe there might be some reasonable explanation. I've attached a screenshot with a few examples using Myriad Pro, Neue Haas Grotesk Display Pro, Minion Variable Concept. In most cases, you can see how the f & i have physically altered, automatically.

Any ideas on how to tell illustrator not to do this?