the other thing to do is just go through the code base later, fixing those kinds of things. i.e., let it go on the pull request, but go through all the code and fix every instance once a month or something.
a few years ago, IIRC, Josh Peek did that for the Rails code base and that one commit got like five thousand "thank you" comments.
A problem with this is it adds useless commit history. If I make a significant change to some code, but then later on you remove some bad formatting/white spaces the latest commit messages for that code block is most likely "removed whitespace" and not something more meaningful.
That, and tasks that are left to be dealt with later are tasks that never get done.
Style guide violations can introduce bugs when moving from one system to another. At best, they slow down communication when someone can't easily understand your code.
There's really no way not to sound like a pedantic jerk when you comment on someone's pull request about such things.
This at least makes the robot out to be the pedant.