It is now a common feature among text-completion functions to allow the user to override the auto-complete and auto-correct suggestion by backspacing over the first character. This would be a helpful feature in Protege, as well.
A problem arises when it happens that the expression one is typing into the text box begins with the same letter as a previous expression but is in a different case. For example, if one uses the class expression editor to type an expression beginning with a capital H (e.g. for a class) and immediately subsequently tries to type an expression beginning with, say, an object property with a lower-case H (e.g. in the form hasProperty), the auto-complete function will capitalize the first letter as in the prior expression and not allow you to make it lower case without first typing more than one character, moving the cursor, backspacing, then typing the lower case character. (this only occurs when there is no previous lower-case expression in the cache)