Before ModBot, if I wanted to give away keys without lurkers taking them it would actually result in more posts. Quote if you want the key etc. It also adds a very useful layer of accountability and transparency which isn't there with manual giveaways. Once the excitement of having a new method to give gifts wears off, and when everyone has learned how the system works, the number of posts pertaining to ModBot will dwindle. I see nothing wrong with the marked increase in generosity surrounding the summer sale that ModBot -- in large part -- has helped facilitate, though.
Stump already created a separate thread for the ModBot FAQ and has told posters to refer to it when asking questions, but as the bot itself serves to replace the traditional methods we used to hand out Steam keys in the Steam thread (yes, was never in a separate thread), I don't see why that function would need a separate thread.
The reason you don't see many other complaints has nothing to do with Stump being an admin; rather, it is because appreciation is the standard human reaction when someone uses their own free time to make life easier for yourself and others while expecting and receiving nothing in return.