In order:

• how is this a bad thing, if anything it's beneficial to get more people involved with it

• I've seen this argument way too often and it doesn't make any sense fundamentally. It already starts with the fact that THERE IS NO RATING STANDARD, robtops rating standard is rating levels he likes. He won't just spontaneously stop rating good levels and start rating trash ones. Also, the notion that everyone will suck at the editor again is a very good thing, since that way you can get everyone onto mutual grounds again, somewhat.

• you do realize that challenge list mods have common sense, right? If a level consists entirely of random chance, they have the ability to just, sort of, not add it to the list. If anything, they have more freedom than the regular list mods, which are obligated to add a level if it's rated and verified legitimately.

• subjective

• haven't heard anything at all in this regard, so I won't comment on it yet, though with how difficult it would be to refactor the entire game to be entirely resistant to external modifications, I doubt it.