Found steps to reproduce the bug: (Microsoft Chinese System , Firefox browser Chinese , Twitter Chinese) In the window to send a new tweet, Enter a few Chinese characters, then move the cursor to the beginning of the line, press the down arrow (the cursor will move to the end of the line), then press Enter. At this point the cursor should wrap, but not.(There is a new line created, but the cursor does not move down). This bug has been around for a long time, causing trouble for me and greatly affecting the user experience. Chrome does not have such a bug, I hope you can fix it. Thank you