I am aware of the warning, but it seems like the warning only pops up once if you are selling many rares.
It only pops up once per card position slot.
For Example, if I were selling all my SoD's it would show up once for the first one, but not again for the rest. Then, my SoG's would move up to that position, and if I wasn't paying attention it would sell them, as well without a warning.
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http://imageplay.net/)
Also, if you switch screens it remembers the position you were clicking. Here, if I were selling one of my Squids the warning would pop up. But then, if I go the the Fire tab and click on Fahrenheit the warning would not pop up.
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http://imageplay.net/)
(
http://imageplay.net/)