There is code in place to prevent posts that look like this:
Neat. And when you add another (regular) word, the code recognizes the person is probably not shouting and reverts the capitalization? Luckily people who shout aren't so clever.
They are generally so angry on the internet that they explode in a fit when they realise they will need to work around the inconvenience of the anti-shout mechanism.
It's fairly simple code, and a fairly simple workaround, yet it's super effective.
That is not a bug.
There is code in place to prevent posts that look like this:
"
LOOK AT ME, I'M SHOUTING BECAUSE I'M VERY IMPORTANT AND YOU MUST READ MY POST BECAUSE THE ALL CAPS MEANS THAT IT IS MORE IMPORTANT THAN YOUR POST.
"