I started working on an answer and first just typed three lines of arithmetic expressions with numbers into the edit box. When I later returned to the page and the content of the edit box was auto-restored, I got a warning asking me not to shout in all caps. There weren't any uppercase letters, only numbers and operators. The condition for this warning should be not only that there are no lowercase letters but also that there are at least some uppercase letters.
Added by A.K.
Here's a screenshot of how something like that happens.
Update: This just happened to me again.