If someone wants to express their gratitude, who are we to ridicule that person?
AFAIC, I don't listen to anyone who uses child-like opinions without any constructive criticism that concerns the material ... usually those that contains third-grade words like "sucks!" or tries to sneak a side comment about the designer's intelligence or competence.
Then again, you go to any fan web site's message board which are moderated, and they tend to lean favorably toward the favorite product or line.
On this board, it leans favorably toward d20 in general. Only once in a great while someone tries to ridicule the system and the gamers who use it, only to be defended by many who are in support of the system.
Then again, I am probably displacing my own personal experience. I got a hardlined father who rarely praises me but always criticizes me. The most common image of my parent always bear a disappointed look. I have to dig deep in my memory to recall if ever he was proud of me.
Sometimes, we gamers took the game designers for granted. I mean, they're not out to win some prestigious Pulitzer or Hugo Award for their literary works. We just buy their games and play. If you feel the need to praise the author, don't hesitate. They might want to hear their time and energy is being invested well.