You are allowed to edit even a single character in the title of a question. I recently did this (without edit privileges) for a question that had a confusing (yet obvious after reading the question) typo in the title.
While I was there, I figured I'd capitalize the first letter of a sentence in the question body that wasn't capitalized.
The problem is that this edit was rejected for being too few characters. The cure was to start over, re-edit the post's title, and then edit even fewer characters in the question body: 0.
This makes no sense to me. If a one-letter edit to a question title with no edits to the question itself is allowed, then shouldn't such a title edit with a few characters changed in the question also be allowed?