The Desmos text entry boxes have the lovely feature many code editors do: autopairing delimiters. It even smart-wraps delimiters; e.g., if you enter the text "x^3 - 1", highlight it, and press the "(" key, the expression is correctly wrapped with round brackets and the cursor is placed at the end of the expression (rather than replacing the entire selection with a single round bracket, the usual behavior in most contexts).
More than one student asked whether it would be possible to build such functionality in WeBWorK's text entry boxes. What do you think? I have no idea how difficult such a thing is to do, or do well.