only allow this to happen if the surrounding area also hasn’t been interacted by anyone else (maybe like a 5x5 around the pixel) to be undone by the eraser

What's the reasoning for this? One of my use cases would have been that I had started to draw something then realised that someone else was drawing next to me, so I'd wish I could have a way to quickly move my thing out of the way. Another one was with a collaboration on a template and in the end trying some adjustments because the template was unsharp. Which was essentially overdrawing other people's pixels just to see how it looks, then perhaps reverting some of those.