Parentheses Bug/Feature, by Chris Holsapple
[Excerpt from a handwritten letter.  -jkh-]

Something neat I figured out long ago (3/90); I asked Bill Wickes
about it & he said it wasn't planned this way so it's an interesting
bug/feature.  Also, he never heard of it before, so I was happy I had
discovered something about the 48.

Put 'ã' [pi] on stack.  Press û [square root].  See 'ûã'.  Press and
hold  [down-arrow], tap ON, then release both keys.  The time between
steps should be quick, before equation writer mode is activated.
[Note: if you see the display blink, you weren't quick enough. -jkh-]

This puts you into a mode where all ( ) are shown for û, ö [/], and
y^x, none of which normally show ( ), regardless of flag -53.

To get out of this mode, get into equation writer and out again.

[Aww, shucks; they "fixed" this, and it doesn't work on the Rev J.  -jkh-]