My favorite MOOcode idiocy is the utter lack of any sort of commenting structure. Not only is it traditional not to comment MOOcode, but commenting your verbs (Programs are 'verbs', since it is a virtual environment you're scripting) actually slows them down. Since any comment you put in is just a string that doesn't do anything, it gets parsed by the MOO server, costing your verb precious ticks. This isn't a problem in most verbs, which are small, but it is precisely the long and relatively complex ones you'd want to comment. (Or would want commented.)
I do like MOOcode, though. It could be better, but it works quite well for what it's supposed to be. It's also relatively easy to learn and get into, and it is quite intuitive. It makes for a good introduction to programming, since you're working in a social environment (if it's a good MOO), have access to all the sample code you could want, and an incentive to build cool junk to play around with with your friends.
Perhaps the highest praise that can be awarded to MOOcode, however, is that it is a wonderful introduction to the concept of Object Oriented programming. Not only is MOOcode object oriented, but a MOO itself is nothing but a bunch of character-objects in room-objects interacting with and creating other kinds of objects using programs and data stored on objects. You just have to get newbies on to some real languages before some of the bad habits set in.