Shared structure is not reflected in the printed output; if the output is parsed back in, fresh objects are created for all literal denotations.
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Circular structure is not printed in a readable way. For example, try this:
{ f } dup dup set-first .
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Floating point numbers might not equal themselves after being printed and read, since a decimal representation of a float is inexact.
On a final note, the short. and pprint-short words restrict the length and nesting of printed sequences, their output will very likely not be valid syntax. They are only intended for interactive use.