Is there any reason, why was it set this way?
On my laptop, I use BBCode editor, which actually writes all tags in uppercase letters.
When I try to post any text formatted like that, it won't parse.
Surely, I found a fix, by going to ACP>Custom BBCodes and I added uppercase tags in " Custom BBCode Aliases (Optional)", for couple of tags, I'm using right now.
But, I really don't want to through every single BBCode, adding uppercase options.
I could also switch to different BBCode editor, which uses lowercase tags, but I think, this issue should be simply adjusted in IPB ACP.