The other thing is its far easier to proofread someone else's work than it is your own... no matter whether you are stephen king or a new writer just starting out, your brain knows what your own writing is supposed to say and literally doesn't see the comma the wrong side of the speech marks, or the fact that you've written their instead of there
Comma splices are an absolute bastard. I struggle with them chronically and can usually only see them when highlighted to me. I've read countless articles on the subject but it's simply one of those things that doesn't 'stick' for me. It's a real problem. I'm embarrassed sharing work knowing these likely exist within.