Having a messy and complex git log is not only about the visuals though. It can make it a lot harder to track down when/where/why bugs and problematic code was introduced. It makes both git bisect and git blame less useful.
Exactly. The canonical reference to how a git log should look is the Linux kernel, since git was written for it: https://github.com/torvalds/linux/commits/master Bisect and blame are amazing in that repo.