Comment 2 for bug 1375122

Unfortunately, C-j is only possible from the previous line, and I tend to jump around the code quite a bit. When I come back wanting to e. g. insert a new line into a matrix, I have to either go to the line before the one I have inserted and press C-j from there, or press TAB repeatedly and align the remainder with spaces. This is completely unintuitive and inconsistent relative to other modes (c++-mode, js-mode, emacs-lisp-mode etc etc, which all move cursor to rightmost sane indentation when pressing TAB). Pressing C-j on the line I want to indent produces a newline and lots of spaces on the line after the inserted one.