I've recently browsed through the wiki for the first time. The LDing guide is W-A-S-O-M. Now, the part about good tips and common mistakes sums up almost everything about what we explain to newer designers in our reviews - "make it longer, avoid cutoff, playtest more", all of these. Shouldn't there be a note in the rules saying that if you're unexperienced with both designing and playing levels, you should read this guide? Shouldn't be a section about level designing added to the rules? Maybe this could help to reduce bad levels on the portal!
EDIT: A few parts in the guide are a bit dogmatic, especially the part of "what tiles fit with which theme?" and all that. I recommend there to be a notification that many tiles can be used in much bigger contexts than it seems, and that these are just raw guidelines on what to do and what to avoid, because: just like in chess, great LDers mostly are really great because they can free themselves from the trammels of dogma.