The person you're replying to wasn't trying to say you meant to invest on margin but that what you are doing is the same as investing on margin. When you do ma

The person you're replying to wasn't trying to say you meant to invest on margin but that what you are doing is the same as investing on margin. When you do margin trading you take on debt to allow you to buy more stock. In your case, you aren't actually "taking on" debt technically, but you choose not to pay it off so that you can buy more stock. After all, the scenarios break down to debt + more stocks or no debt + less stocks. Obviously there are some differences, but I hope that explanation of the analogy made sense. The point is, by investing money instead of using it to pay off debt you are increasing your risk and reward whereas when you pay off debt you decrease it.