It's exceedingly annoying since 90% of the items I collect are 7*+, especially as a summoner with eggs and candy drops as well. Every single time I want to sell some worthless trash, or feed a pet, the game pretends like that would be a bad idea for some reason.
"Woah, am I accidentally eating a useful pet, or selling an item I could exchange for Excubes or Photons? No, it's not a real rare, shut up game."
So, if I could remove the warning entirely, that'd be nice, since I already completely disregard it by mashing buttons as quickly as possible. 7* gear is by definition worthless, so it informing me that I'm selling garbage is wholly unhelpful. Ideally I could change it to 10*+ so if the warning does appear, I know it's something to care about even the tiniest bit.