I'm sure you please lots of people to no end with such a keen eye for typos and your kind service to always inform those in great need of your service. :)
Seriously though, I probably would have gone the rest of my life saying "that" when I should be saying "who". And I'll probably still do it countless times, but I catch myself here and there now and can only thank you for that, otherwise I doubt I would have ever known. Who else would have been so helpful as to show me my error there? :)