The thing is that writing a good commit message for future people doing `git blame` is only worth it if it's a line of code which someone in the future will look at and need to know why it was changed from its previous form to the current form.

Well what about this example: I removed a few lines of code and explained in the commit message why I thought it was correct to do that. If somebody (possibly me) comes looking for that code and realizes it's not there, they'll be much happier to see some sort of explanation rather than a "removed lines" message.

Regarding commenting in the code vs. in the commit message, sometimes I copy-paste my explanatory comment if there is one into my commit message.