I've had an idea for some time now to create a website that would act as a better codereview.stackexchange.com. It would incorporate some of the features of the GitHub Pull Request system like inline commenting and reactions.
I arrived at this idea from two directions. The first direction is that I sometimes try to code review some of the questions over at CodeReview SE, and the whole thing feels unergonomic. I dislike scrolling up and down to check the code and constantly losing track of the things I'm reviewing. This is where I think inline commenting would help. Also, there is not a lot of room for discussion. You only get those comments below the review, where you only have a few characters to argue your point. The second direction is that I produce code snippets (programming homework, short snippets at work, etc.) which I would like to submit for review. I don't always want to submit it to the entire internet for review. I just want to get a private link to the code review, which I can share with my colleagues so they can review it. Kind of like a reviewable PasteBin.
Some of the features I would like to add: importing files from GitHub for reviewing and users could import their unanswered CodeReview SE questions for another review.