Yeah, that's the rule.
It's very helpful for avoiding duplicate posts and searching for threads in the FR archives.
Your innocent change is no big concern.
And you can usually ADD minor changes to the original title for clarification.
The major taboo to be avoided is radically changing the title to something completely different.
Some fanatics try doing that all the time to scream their own opinion as a headline when they should really just be making their comments in the "your comments" box. Those are a pain in the neck, because then you wind up with the same article posted 50 different times by 50 different people with 50 different titles. That's no good.
Great thanks very much to both of you for the input. Freepers are the best!