I had a couple of other people mention the same thing, so I'll just post about it here for clarity's sake. The left/right bracket keys refer to the [] characters. Some people think it's talking about () or <> but none of the inputs require using shift, which those characters would. I could try to have it parse additional characters that require using shift, but that would be more effort than I'm willing to put into this.
It's not even that, it's simply that some keyboards (like mine) don't have those keys as a standard. For example the open brackets on my keyboard is ö while the close brackets is -, while semicomma is '. Sticking to simply the QWERTY buttons that are the same (for the most part at least) would have been better so people don't have to go mashing every key on their keyboard hoping to find the right one