Keywords communicate their associated parameter's role. Since the keywords and parameters are together at the head of every method, the reader can easily understand a parameter's role without relying on the name. Smalltalk doesn't have a strong notion of types. A set of messages sent to an object appears nowhere in the language or programming environment. Because of this lack, there is no direct way to communicate types.
Classes sometimes play the role of types.
If there is more than one parameter with the same expected class, precede the class with a descriptive word. The conflicting needs of formatting to produce both few lines and short lines is thrown in high relief with this pattern. One extreme would be to place all the keywords and arguments on the same line, no matter how long the method. This minimizes the length of the method, but makes it difficult to read. If there are multiple keywords to a message, the fact that they all appear is important to communicate quickly to a scanning reader.