The problem with this approach is, the blame before and after the ignored wouldn’t make any sense to the viewer if he didn’t know about ignoring the formatting commit. Also, you will need to configure that for every clone. Since tree diffing algorithms are pretty well known these days, I don’t know why there hasn’t been any real effort to implement a git plugin that can chase syntax tree node changes instead of doing string diffing like it was the 70s. Syntax parsers are so easy write now and surely the tree node changes can be cached. Your usual diff/patch tooling wouldn’t work for this kind of diff, but that’s just an option away when you need them back.
This is a nice feature, but I do wish that .git-blame-ignore-revs was automatically applied, similarly to .gitignore and .gitattributes. Hopefully there are plans to do so in a future Git release?