I watched a video (I believe it was a talk by the author of radare2) of how to increment machine code in radare2 very easily, simply by hitting 'c' and then using + and - to respectively increment and decrement machine code.
However, now, when I hit v and then p to get to the visual mode where I can see disassembled code, I hit c, I can move the cursor around, but I can't increment and decrement machine code any longer.
Am I remembering this incorrectly? Clearly I need to take better notes, because I find it hard to find this information in the myriad of online "cheat sheets" and tutorials that always seem to talk about something else than what I'm really after.