When I am rejecting a suggested edit, I like to use the "custom" box to give more directed feedback to would-be editors. But there's a usability problem there that disrupts my workflow.
After I've finished typing and press the Enter key, I expect the form to be automatically submitted just as if I'd moved my mouse down to click the "Reject" button.
Instead, the Enter key currently returns to a new line, which is useless considering that the suggested edit rejection reasons don't show line breaks.
I realize that the standard behavior of the Enter key is to insert a new line, but having it trigger a submission for something that doesn't support multiple paragraphs is not unprecedented. We do precisely this for the comment box already. You have to press Shift+Enter in order to return to the next line. The "custom" field in the suggested edit rejection dialog should work the same way.