I know when I was a group leader (not the boss), I liked all the workers equally....but just because I liked them equally, didn't mean that there were some whose abilities stood out more than others.

It's not something that I would have ever made known in a public way, but your boss probably didn't even think that's what he was doing with his words.....& maybe in fact he really wasn't doing it even though it came across sounding that way. Unfortunately, some people are as oblivious to what they say/write as we are sensitive to it.

Best thing is to not focus on comparisons & just focus on doing your job to the best of your ability because that's what's going to make the difference & it's obvious that your boss does like the work you are doing even though it may not be as outstanding as a coworker you are feeling compared to. I have found in life that there is always someone who is going to be better than I am no matter how hard I try with my perfectionist personality.....so I just accept what is & enjoyed my work & the people I worked with.

Just to let you know, it's normal to feel the feelings you experienced when reading your bosses notes......it takes the processing of your thoughts & listening to your logical mind along with your emotional mind to be able to put it all in perspective.....which is what you are doing here & did very well in your initial post.