Distant Planet: Probably should be banned. Camping exploits on this stage are a bit heavy: take Sonic for example. Get a lead on someone, and go to the lower end of the walkoff. If someone approaches you from the left, spin jump to the right and get on grass platform. If they go off the grass platform on the right side and come down towards the walkoff edge, run up the walkoff. If you are at the top of the walkoff and they come, spin jump over them (easier to get away with this because you already start at a higher vertical position than them due to the slope). If they are trying to stop you from going over them from where you are at the top of the walkoff, you now have a slope to run down (most characters if they are trying to stop Sonic from going over them, have to go airborne with a full jump or more to do so. Doing this allows you to easily go under them, even if they fastfall) From the grass platform, you can maneuver back over it, under it to the slope, under it back to the platform, etc.
Or take Wario: I can start from the top of the walkoff, jump and Bike to reach a position nothing but maybe a Sonic Spring or a Pikachu thunder could reach me, while having the flexibility to maneuver completely around to my liking. I can go to the right, not touch the ground, go past the grass platform completely, pass by the edge and choose to grab it or keep going, have the option to grab the slope edge or go onto the slope without grabbing it OR going through the bottom of the grass platform OR deciding to go back and grab that grass platform edge, etc.
If my opponent wants to stop most of those options, and heads towards the grass platform, while I am up in the air I also have the option of going back to the top of the slope. It's easier for me to reach there than my opponent because the top of the slope is at a noticeably higher position than the grass platform. Another thing that benefits me is that if you start on the grass platform, and want to chase me to the slope, you HAVE to go airborne in some way or form to get off the platform and get towards the slope. Going into the air, where Wario moves faster horizontally than 95% of the cast, means you can't use a fast run or dash to keep up with me. This "forced" air entry is a big reason why he's extremely gay on Norfair (and to a lesser extent Brinstar): how can you catch a character who is almost guaranteed to be faster than you in the air, if you have to go into the air to traverse from platform to platform or from section to section? There's no room for running faster than I move, so you are forced to play my game and come into the air for long enough to be outmaneuvered over and over.
About the rain: the rain as far as camping is concerned is completely double edged. I laugh at the people who see the rain as something that completely destroys camping the slope, because they tend to also miss the fact that the rain takes away a lot of offensive options to stop it. Say I'm on the slope, the rain comes blah blah blah, so I fall to the slope edge. Now what? How can you reach me if I decide to stay on the edge for as long as possible? I'm not talking about constantly regrabbing the edge either wasting LG's, just grab it 1-2 times and sit there. Going the slope way would be dangerous for a lot of characters. You can't sit on the slope and throw projectiles down. You could go off the grass platform right side and move through the air to the slope edge, but that still allows the person on the edge to move up to the grass platform with no real resistance on your part (that and now you're under the grass platform trying to get somewhere).
Distant Planet basically is a twisted version of Cat and Mouse: the Mouse has to catch the Cat. Outdoors. With trees and sh** in the way. GG Mouse... GG