I have never experienced this occurrence, yet I have had several people describe it to me. I heard it again today and thought I'd find out if anyone here has experienced it or heard of it. The person today is using 2000, but I don't know the service release; I don't know what version/service release the others are using.
Here's their unanimous description: "I'm typing along and glance up to see that the font has changed to a smaller size." They insist that it happens while they are typing continuously, and that they are not moving through the text with the arrow keys or mouse, then returning to their typing. They also insist that this happens in a brand new document with no other text in it. Of course, this doesn't happen all the time, so it's going to be almost impossible for them to show me.
My thought was that while in the process of typing, they may have moved back to correct an error or unknowingly moved the insertion point away and then back to what appeared to be the same location but which was actually "outside" of text which they had previously formatted with the larger font. They insist they have not done this.
I'm anxious to hear your responses.