It's pretty good. There are two things I'd say.
One, this part:
It's impossible to follow every best practice all the time. Code sins are those things we do to our code that are either so horrendous that they can't be borne, ...
they seem confusing. You are mention the bad things in the title, but then go to "best practices" and immediately drop it. I'd somehow link the idea that if we can't do the best, let's not do the worst.
The second thing is I'd like to see one or two concrete examples of what is bad. I don't think you want to surprise people with the items. Tell us a couple of the sins that you'll correct in this abstract so that the coder that does x or y, will come find out what they can do instead.