Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You compared two values that cannot be put in order. Less than and greater than ask which one comes first. That question only makes sense inside one kind. Two numbers can be compared numerically. Two texts can be compared byte by byte. But a number against a text? Which comes first, the number one or the letter a? There is no honest answer, and inventing one would be coercion, quietly turning one kind into another. Rush does not do that. A quoted number stays text. So one less than a quoted two is refused, and so is one less than the letter a. Equality is different, because it has a fair answer: two values of different kinds are simply never equal. So one equals a quoted one is false, and one not equal to a quoted one is true. No error there. The message shows the kind on the left and the kind on the right. The fix: make both sides the same kind before comparing, convert the text to a number or the number to text, whichever you really meant.
Text from the Rush engine's error catalogue.