Sentence/command error rate (rate of 100% correct sentences/commands that don’t need any editing or re-attempting) is a decent proxy for this. It’s no silver bullet, but it more directly measures how frustrated your users will be.
If you really wanted to take care of the issues in the article, you could interview a bunch of users and find what percent of the, would go back and edit each kind of mistake (if 70% would have to go back and change ‘liked’ to ‘like’ then it’s 70% as bad as substituting ‘pound’ for ‘around’ which presumably every user will go back and edit).
The infuriating thing as a user is when metrics don’t map to the extra work I have to do.