I personally don't consider buying an item from a cheaper server and then reselling on your higher-priced server by itself to be a bad thing. It's kind of like buying an item from NPC and reselling high. If someone's willing to put in the time and legwork, kudos on whatever profit they make.

I imagine SE had thought of this possibility when deciding whether or not to allow access to MBs using the world-visit system. So assuming they are OK with the situation above, outside of their normal bot/RMT bans, how would you expect SE to deal with this particular situation? I feel that even if RMT is ruining particular markets, it's still far more beneficial to allow players to the cross-world market boards for purchses.

I'm not trying to say the situation doesn't exist or isn't bad (honestly, I've not noticed it, but I've also not been playing much lately..so who knows!). RMT in general screws with prices, but they also go hand-in-hand with MMOs. They will always be a thing, and it seems they always have the upper hand.