Another approach would be to add a new "extra property"
or metadata element which will say "don't remove duplicates".
I mentioned variable `icicle-transform-function', whose
most common values are `icicle-remove-duplicates' and
nil (which means don't remove dups).
(Like such a variable, completion metadata is an
aggregate operation: it applies to a set of completions,
not to just this or that completion.)
`icicle-transform-function' is applied to all candidates,
and it can do anything.
I do think it's questionable, though, to include
completions that are hard to distinguish.
Don't confuse looking different in *Completions*, at the
outset and always, with easy to distinguish. There are
other ways to make them appear different - from mode-line
to ephemeral appearance changes in *Completions*. There
is more than one way to skin this cat.
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