I attempted to post an all caps reaction to a horrific story here. The post was apparently automatically converted to lower case, which ruined the effect of the post. (Not that I’m complaining that it was a particularly brilliant post, mind you.)
I figure this is a feature to keep people from posting in all caps, all the time. I’m not saying I want to see lots of people doing that, but it bothers me that in the rare cases when it’s a good way to get a message across, it’s not allowed.
I learned a long time ago that all caps is the same as someone yelling at you. Is that the message you were trying to convey? 
Aaaaaaaaaaaaaaarrrrrrrrrgggggggggggg
Well holy crap, it does convert them to lower case.
It shows up as lower case on preview.
Hmmm…
HMMMM…
Well, it does say this is the place for test posts, so…
TEST TEST test
Writing along normally then GOING ALL CAPS by shifting
Same thing but USING CAPS LOCK
STARTING on caps lock
STARTING on shift
And now a message from Roger Daltrey and Howard Dean:
YAAAAAARRRRGHHHHH!!!
YAAAAAARRRRGHHHHH!!!
AAAAAAAAAAAAAARRRRRRRRRGGGGGGGGGGGGGG
Huh. Seems to work for me. Maybe a profile preferences default setting?
TESTING AGAIN
If The Entire Post Is In Caps It Appears That The Board De… Caps… All But The First Letter Of Words. It Doesn’t Work If You Have A Quote Or Any Lower Case Letters.
aaa
AAAAARRRRRRRGGGGGGGGGGHHHHHHHHHHH
IF THE ENTIRE POST IS IN CAPS IT APPEARS THAT THE BOARD DE… CAPS… ALL BUT THE FIRST LETTER OF WORDS. IT DOESN’T WORK IF YOU HAVE A QUOTE OR ANY LoWER CASE LETTERS.
Well…in the linked thread, yes.