You will always get the odd observer that you end up thinking "what was he watching". I assisted a L3 who I thought I had a great game, the observer thought otherwise and tore him to pieces after the game. Ironically I got my L3 the next season and got the same observer at the same club, and I just could not believe his comments after the game. He killed me, and even with ridiculous comments like he never heard me all game, whereas anyone that knows me is well aware that I am extremely vocal on the pitch (to the extent that players tell me to shut up
). Like I'd been with the referee the previous season, my assistants were aghast after he had left, but ultimately there isn't a lot you can do about it. What I would say is we were both first year L3s and there has long been a theory that some observers mark these lowly to keep their average down, knowing that it won't get them demoted, but there is a massive difference between marking them lowly and completely killing their confidence.
Thankfully though these are few and far between (and this one was booted back to county level the following season), the vast majority of observers are very fair and are looking to actually develop the referee rather than looking for faults.