Good commits are not a requirement form bisect. I commit when I think something more or less completed, or I want to start a major refactoring and I'm afraid I might need to revert it.

I don't always check if commits are buildable, PR should be, because that is what is merged to master and tip of master should be buildable.

If a commit isn't buildable then when you get to it with bisect you have to skip. If this happens once in awhile it's not fatal, but it's sure not helpful