The confirmation codes are necessary for guest posts due to spambots flooding the forum. As Tony E stated, register and you won't have to deal with them.
Uppercase letters are easier to read then lowercase letters (eg. 1 and l and I).
So you may be glad that you do not have to think about that.
On some sites it is really not easy to see what you have to type.
Case sensitivity in the input isn't going to make it harder. If a spam bot gets to the point where it's entering data, it's probably already figured out what to insert.
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